Guaiacum

What is Guaiacum?

A guaiac stool test card turns blue when heme from blood helps hydrogen peroxide oxidize alpha-guaiaconic acid, a lignan from the resin of the lignum vitae tree. That color change, described in Beckman Coulter's Hemoccult SENSA package insert as the formation of "a highly conjugated blue quinone compound," is the one task guaiacum still performs reliably in medicine, and it performs it on paper, not inside a body.

Guaiacum is a small genus of slow-growing trees and shrubs in the Zygophyllaceae, the creosote-bush family, native to the Caribbean, southern Florida, Mexico, Central America and northern South America. Two species carry the medicinal tradition: Guaiacum officinale, common lignum vitae, and G. sanctum, holywood lignum vitae. The 1911 British Pharmaceutical Codex described the heartwood as dark greenish brown and "heavier than water," and lignum vitae ranks among the hardest commercial timbers, at about 4,500 pounds-force on the Janka scale. Ship builders and engineers used it for propeller-shaft bearings, pulley sheaves and bowling balls, and a 2002 CITES proposal still listed those uses.

The same codex put the resin content of the heartwood at 20 to 25 percent. German phytotherapy references give about 25 percent in the dark heartwood and about 3 percent in the pale sapwood. Commercially, the resin was "melted out" by heating logs and collecting what ran off. Cleaner natural "tear" resin was preferred and, even in 1911, scarce.

Three different products are sold under the name today: heartwood chips and shavings (for tea and, in Germany, for flavoring liqueurs), the resin itself (as lumps, powder, tinctures, a food antioxidant and a laboratory reagent), and homeopathic dilutions made from the resin.

Common Names

Lignum vitae ("wood of life"), lignum sanctum or holy wood, guaiac, guaiac wood, guaiacum wood, gum guaiac, gum guaiacum, guaiac resin and guaiacum resin. Hutten's 1519 treatise reported that physicians also called the wood "manus Christi" and "gratia Dei." William Turner's 1568 English herbal called it "Diet woode," after the starvation diet that went with it. Spanish names include guayacán and palo santo. The genus name comes from Taíno, and G. sanctum is the national tree of the Bahamas.

Three look-alike names belong to other substances. Guaiac wood oil, a perfumery oil, is distilled from Bulnesia sarmientoi, a South American relative also sold as "palo santo" and "Argentine lignum vitae." Guaiacol is a single phenol first isolated by Otto Unverdorben in 1826 and named after guaiac. Guaifenesin, the cough expectorant, is a synthetic glyceryl ether of guaiacol and contains no guaiac resin.

Primary Active Compounds

• Alpha- and beta-guaiaconic acids, together about 70 percent of the resin according to the 1911 codex. Alpha-guaiaconic acid is the lignan furoguaiacin (Nakano and colleagues, Journal of Natural Medicines, 2016) and is the chromogen that turns blue on a stool test.

• Guaiaretic acid, about 11 percent of the resin in the same codex. Nordihydroguaiaretic acid (NDGA), the compound behind chaparral's liver warnings, is named for its chemical relationship to it.

• Guaiac beta-resin, about 15 percent, plus small amounts of guaiac yellow and vanillin.

• Further lignans: Nakano's group purified six from commercial guaiac resin, including dehydroguaiaretic acid, meso-dihydroguaiaretic acid, furoguaiaoxidin and nectandrin B.

• Triterpenoid saponins in the non-resin parts: guaiacins A and B from the leaves (Planta Medica, 1989), guaianin R from the bark (Natural Product Research, 2004) and guaianin O from the flowers (2010).

Key Note

The decoction that 16th century Europe bought as a cure for the "French disease" was made from the wood. What modern labs, food makers and homeopathic manufacturers use is the resin. What a herbal shop sells may be either, may come from a third Guaiacum species, or may be Bulnesia sold under a shared trade name.

The rest of this issue sorts the history from the chemistry, and both from what a buyer is actually being offered.

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Primary Functions & Benefits

Guaiacum has no demonstrated benefit in any controlled human study of oral use that I could locate. It has two real functions, neither of them therapeutic, and a set of claimed ones that rest on rodents, rabbits and cell cultures.

Real function 1: a diagnostic reagent. Guaiac-impregnated paper detects the peroxidase-like activity of heme. The Minnesota Colon Cancer Control Study (Mandel and colleagues, New England Journal of Medicine, 1993) randomized 46,551 people aged 50 to 80 to annual screening, biennial screening or no screening, using six guaiac slides per screen. Thirteen-year colorectal cancer mortality was 5.88 per 1,000 in the annual group against 8.83 in controls, a 33 percent reduction; the biennial arm (8.33) did not differ significantly at that point. At 18 years the biennial reduction reached 21 percent (rate ratio 0.79, 95 percent confidence interval 0.62 to 0.97). Every person in that trial benefited from guaiac without swallowing any.

Real function 2: a food antioxidant and flavoring. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) lists guaiac resin as INS 314, functional class antioxidant. In the United States, "Guaiac" (G. officinale, G. sanctum and Bulnesia sarmientoi) appears on the 21 CFR 172.510 list of natural flavoring substances, with no limitation stated. Section 5 covers how much of this anyone eats.

Claimed: rheumatism and gout. This is the surviving herbal indication, and the homeopathic one. Duwiejua and colleagues at the University of Strathclyde (Journal of Pharmacy and Pharmacology, 1994) gave rats an aqueous ethanolic extract of G. officinale by mouth. At 100 milligrams per kilogram it did nothing in carrageenan paw swelling; at 200 milligrams per kilogram it reduced that swelling and, in adjuvant arthritis, acted only on the chronic phase. Williams, Jacob and Levy at the University of the West Indies (West Indian Medical Journal, 2017) found anti-inflammatory and analgesic activity in rats given an aqueous bark extract at 16 and 32 milligrams per kilogram, with the route inconsistently reported between sections of the paper. Sarkar and colleagues (Homeopathy, 2014) reported improvement in arthritic rats given a commercial Guaiacum mother tincture and 30C and 200C dilutions. None of these involved a person.

Claimed: blood sugar. Román Ramos and colleagues in Mexico City (Archives of Medical Research, 1992) gave rabbits traditional decoctions of 12 plants used locally for diabetes; Guaiacum coulteri, a Mexican species, produced the strongest drop in induced hyperglycemia. A follow-up found the effect in healthy and mildly diabetic rabbits but not severely diabetic ones. Ibrahim and colleagues (Pakistan Journal of Pharmaceutical Sciences, 2019) reported lower glucose in streptozotocin-diabetic rats given 500 milligrams per kilogram of methanolic G. officinale bark extract for 28 days.

Claimed: infections. In a Mexican screen of 53 plants against Helicobacter pylori (Journal of Ethnopharmacology), a methanolic G. coulteri extract was among the four most active, a group with minimum inhibitory concentrations of under 7.5 to 15.6 micrograms per milliliter. Against Mycobacterium tuberculosis the same species needed 1,000 micrograms per milliliter (Robles-Zepeda and colleagues, BMC Complementary and Alternative Medicine, 2013). Neither is a human result, and neither concerns the two species sold as medicinal guaiacum.

Claimed: sore throat and tonsillitis. The 1911 codex recommended guaiacum lozenges of about 3 grains of resin for chronic tonsillitis. The German Altmeyers encyclopedia still names Tonsipret, a sore-throat product, under guaiac wood. I found no trial of guaiacum alone for throat infection.

Forms & Standardization

No guaiacum product I found states a guaiaconic acid percentage, and none is standardized to any marker compound. What varies between forms is which part of the tree is used and how much resin ends up in the product. Every quantity below describes a product, a pharmacopeial specification or a historical formula, not an amount shown to help anyone.

Heartwood chips, shavings and powder (guaiaci lignum)

The wood of the old Hutten regimen and of modern herbal teas. Resin content depends on the cut: roughly 20 to 25 percent in dark heartwood, about 3 percent in sapwood. German references give 12 to 15 percent lignans for the wood overall. The 1911 codex judged the wood "rarely used" and the resin "preferred." The resin does not dissolve in water, which limits what a water decoction of chips can carry. German phytotherapy texts list an average 4.5 grams of wood a day for "supportive treatment of rheumatic complaints"; that figure comes from monograph tradition, not from a dose-finding study, and appears here as a regulatory-history fact.

Resin (guaiaci resina, gum guaiac)

Sold as dark brown lumps or powder that melts at about 85 to 90 degrees Celsius, dissolves in alcohol and fats, and does not dissolve in water. The 1911 codex set quality markers: good block resin should leave under 8 percent alcohol-insoluble matter and under 3 percent ash, while tear resin carried about 2 percent foreign matter and 1 percent ash. Food-grade resin is covered by a JECFA specification published in 2000 (FAO Food and Nutrition Paper 52, Addendum 8).

Historical tinctures and mixtures

These are recorded as pharmacy history. The 1911 codex listed Tinctura Guaiaci (20 parts resin in alcohol to 100), Tinctura Guaiaci Ammoniata (20 parts resin with 7.5 parts strong ammonia solution, plus nutmeg and lemon oils), Mistura Guaiaci (2.5 percent resin suspended with sugar and tragacanth in cinnamon water) and Confectio Guaiaci Composita, a paste of resin, rhubarb, cream of tartar, sulfur and honey "popular" for gout. The tinctures needed acacia mucilage to keep the resin from dropping out of suspension when diluted with water. The same codex gave 0.3 to 1 gram of resin as its dose range, a figure from a reference that predates any controlled trial of the resin.

Homeopathic Guaiacum

Homeopathic labels name the source as guaiac resin; DailyMed entries list the active ingredient as "Guaiacum officinale resin." Potency determines whether any resin is present in measurable amounts. A 1X preparation is one part stock in 10; a 4CH is one part in 100 million; at 12CH and beyond, dilution passes the point where any molecule of the starting material is likely to remain.

• Boiron Guaiacum granules: sold in 4 gram tubes of about 80 pellets, in potencies from 4CH to 30CH. A French retailer's listing tags them for joint pain, gout attacks and rheumatic disorders; the Canadian listing carries no therapeutic indication and directs 5 pellets three times a day.

• Rxhomeo "GUAIACUM tablet," labeled "HPUS 1X and Higher," with "Rheumatic Pain" under Uses and directions of 4 or 6 tablets three times daily for adults and half that for children from age 2. Its DailyMed entry, last updated January 2016, shows every listed NDC inactivated under an FDA-initiated compliance action.

• Hahnemann Laboratories Guaiacum pellets, for "relief of minor joint pain," with a label line that severe disease needs "a clinically proven therapy."

Topical extracts

One cosmetic study used a commercial G. officinale extract (10 percent dry matter in water and butanediol) combined 1:1 with a Rhodomyrtus tomentosa extract, at 5 percent of a face cream (Section 10).

Which form the human trials used

None. No human efficacy trial of oral guaiacum wood, resin or tincture appears in PubMed under any of the names I searched. The only human dosing data for the resin are safety feeding studies (Section 14).

Food Sources

Guaiacum is not a food, and no diet supplies it in any meaningful sense. The realistic routes of exposure are these.

As a food additive. JECFA set an acceptable daily intake for guaiac resin of 0 to 2.5 milligrams per kilogram of body weight at its 17th meeting in 1973, revising a 1961 figure of 0 to 2.0. That ceiling works out to 175 milligrams a day for a 70 kilogram adult. The Codex General Standard for Food Additives, as summarized in a 2025 Turkish government opinion, allows up to 1,000 milligrams per kilogram in vegetable oils and animal fats and 600 milligrams per kilogram in sauces. The same opinion states that E 314 is not authorized under EU or Turkish food additive rules. For animal feed, US regulation 21 CFR 582.3336 recognizes gum guaiac as safe in edible fats or oils at a tolerance of 0.1 percent.

As a flavoring. The 21 CFR 172.510 listing allows guaiac as a natural flavoring substance in the United States. A 2002 CITES proposal reported that Germany imports an estimated 20 to 40 tonnes a year of guaiacum heartwood resin and chips for its liqueur industry, so a bitter liqueur is a plausible place to meet it.

As a herbal tea or tincture. Wood chips and resin are sold loose by some herbal suppliers. Belgium and Italy, per the Turkish opinion's survey, permit guaiacum wood or resin in food supplements; Denmark lists the resin with a daily amount of 20 milligrams; Germany restricts the wood to flavoring and medicinal use.

As a homeopathic remedy. Covered in Section 4. Above about 12C, exposure to the resin is effectively zero.

On a stool test card. Not ingested. The person collecting the sample is the only one who handles the slide, and the reagent stays on the paper.

Through the skin, at work. Sugai and Okuno reported occupational hand dermatitis from guaiac in a printing paste (Contact Dermatitis, 1980). Woodworkers cutting lignum vitae handle a heartwood that can be a quarter resin by weight.

Is dietary intake sufficient? The question does not apply. There is no requirement to meet.

Who Should Take Guaiacum

Nobody has a reason grounded in human evidence to take guaiacum for any health purpose. Several groups meet it anyway, and a few should know about it.

Anyone booked for a guaiac-based stool test. This is the group for whom guaiacum matters most, and what they need to manage is the test, not the herb. The diet and drug instructions in Section 17 decide whether the result can be trusted.

People with joint pain who are drawn to it by tradition. The tradition is real and centuries old; the evidence consists of rat paw-swelling experiments at 200 milligrams per kilogram and a homeopathic rat study. Rheumatoid arthritis and gout both have treatments tested in large randomized trials. If a guaiacum product is used, it should be in addition to a diagnosis, not instead of one.

Anyone who suspects syphilis. Historically this was the indication. It should not be now. The Centers for Disease Control and Prevention recommends a single intramuscular injection of 2.4 million units of benzathine penicillin G for adult primary and secondary syphilis. The wood never cured it (Section 11).

Homeopathic users. At typical potencies the pellets deliver lactose or sucrose, not resin.

Who might be tested. No deficiency or blood level of any guaiacum compound is measured clinically. The only relevant "test" is the stool card, and for adults at average risk of colorectal cancer, a clinician can explain whether a guaiac test, an immunochemical test or colonoscopy fits best.

Who Should AVOID or Use Caution

Contraindications

• Pregnancy and breastfeeding. No safety data exist for either, and the Natural Medicines content reproduced on WebMD advises avoiding use. The resin also had a menstrual and abortion reputation: King's 1854 Eclectic Dispensatory reported its use in amenorrhea, the 1911 codex listed dysmenorrhea, and historians cite 1793 Virginia court testimony by Martha Jefferson Randolph linking gum guaiacum to inducing abortion. That history is a further reason not to experiment in pregnancy.

• Known sensitivity to guaiac resin, including a history of contact dermatitis from it. Allergic reactions and irritation of mucous membranes, including the digestive tract, are cited in the 2025 Turkish risk opinion from hazardous-substance and herbal references.

• Inflammatory bowel disease, active gastritis or other inflamed digestive conditions. Diarrhea, gastroenteritis and intestinal cramps are the reported effects of high resin intake.

• Untreated syphilis, or a sore, rash or lesion that could be syphilis. This is an infection with a single-dose cure, and every week on an ineffective remedy is a week of possible transmission and progression.

Use Caution

• Lithium therapy. The Natural Medicines content on WebMD rates the pairing a moderate interaction because guaiac wood and resin may act like a diuretic and could slow lithium clearance. That reasoning rests on the herb's old reputation, not on a measured case.

• Anyone preparing for a guaiac stool test, because vitamin C, red meat, aspirin and other drugs can distort the result (Section 17).

• Children. The 1X homeopathic tablet label directs half the adult dose from age 2. I found no pediatric data of any kind for guaiacum.

• Homeopathic mother tinctures and alcohol-based guaiac tinctures in anyone avoiding alcohol. The 1911 tincture was resin dissolved in alcohol.

Critical Safety Point

The disease guaiacum was famous for has a natural course that flatters any remedy. Syphilis can disappear on its own between stages: the first sore heals within weeks, secondary lesions fade, and late damage can surface years afterward. That natural course is exactly what made a 16th century remedy look like a cure, and it can make a 21st century one look like one too. Anyone with a possible syphilis sore or rash needs a blood test and, if positive, penicillin. No guaiacum product, at any dose or potency, belongs in that decision.

Recommended Dosages

Guaiacum has no evidence-based dose, because no human trial has tested any amount of wood, resin or extract for any outcome. The figures below are regulatory ceilings and label facts, kept here so a reader can judge a product, and none of them is an amount to take.

Resin, as a food additive ceiling

JECFA's acceptable daily intake is 0 to 2.5 milligrams per kilogram of body weight per day, about 175 milligrams for a 70 kilogram adult. That is an upper bound for lifetime exposure through food, derived from rat feeding data, not a therapeutic amount.

Resin, as a supplement-list entry

Denmark's listing of guaiac resin carries a daily figure of 20 milligrams, according to the 2025 Turkish opinion's survey of national lists. Turkey itself keeps the resin and its extracts off its permitted food-plant list.

Wood chips and teas

No tested dose. The German reference figure appears in Section 4 as regulatory history.

Tinctures

No tested dose. Historical tincture strengths were 20 percent resin, which puts a large amount of resin in a small volume.

Homeopathic preparations

Label directions are not doses in a pharmacological sense. A 1X tablet contains resin; a 30C pellet does not.

Duration

I found no study linking any length of use to any benefit. The longest human exposure I found is a safety observation in 11 people over 18 to 104 weeks, reported by JECFA and described in Section 14.

Timing & Administration

No timing advice follows from the evidence, because there is no benefit to time. A tea and a tincture are not interchangeable, since only alcohol carries the water-insoluble resin (Section 4). The timing that does matter belongs to the stool test: the Hemoccult SENSA instructions start the drug restrictions 7 days before the first sample and the food restrictions 3 days before, and ask that slides be returned within 10 days of the first sample.

Timeline of Effects

Nobody has timed an effect of oral guaiacum in a human being. With no measured onset or peak, a reader has no evidence-based trial length to give it and no point at which failure to respond means anything.

The animal timelines are short. In the Duwiejua rat study, extracts were given before inflammation was induced, in models that run from hours (carrageenan swelling) to the weeks-long chronic phase of adjuvant arthritis. Ibrahim's diabetic rats received bark extract for 28 days. Neither translates into a human schedule.

The only human study with a timeline involved skin, not swallowing. Zhang and colleagues (Journal of Cosmetic Dermatology, 2024) had 30 adults with acne and sensitive skin apply a cream containing 5 percent of a 1:1 G. officinale and Rhodomyrtus tomentosa extract mix twice daily. Comedones fell 12.5 percent by day 7 and 50 percent by day 28; papules fell 16.7 and 30.7 percent. There was no control group, so those changes include whatever would have happened anyway.

Benefits of Taking Guaiacum

There are no proven benefits of swallowing guaiacum. What it has instead is a 500-year paper trail, with names, dates and prices that can each be checked.

By 1508: arrival in Spain. Guaiac wood reached Spain from Hispaniola by 1508, according to Bičak's 2023 study in Social History of Medicine. The Taíno decoction met a European disease epidemic that had spread after 1495, and a widely held belief that God placed remedies near diseases made a New World wood for a supposedly New World disease persuasive.

1518 to 1519: Hutten. Ulrich von Hutten, born April 21, 1488, had by his own account undergone eleven topical mercury treatments. In autumn 1518, during the Imperial Diet at Augsburg, he took the guaiac decoction, and in April 1519 Johann Schöffer printed his De guaiaci medicina et morbo gallico in Mainz. His regimen: purging, a closed and continuously heated room, a diet reduced until the patient was "as thynne with hunger as maye be possible" (in the 16th century English translation), the strong decoction at 5 in the morning and 7 at night, and a course of at least 30 days. Thomas Paynell's English translation, Of the wood called Guaiacum, followed in London in the 1530s.

What happened to Hutten. Urs Leo Gantenbein's 2025 paper in Medical History, drawing on Hutten's letters, reports that the guaiac course brought temporary improvement and that "relapses were not far off." Hutten died on the island of Ufnau in Lake Zurich, most likely on August 29, 1523. A skeleton excavated near the island's church in 1968, re-examined by a University of Zurich team from 2016 and identified as Hutten's (despite female sex markers, which the team attributes to a possible intersex condition), shows treponemal lesions in a pattern Gantenbein reads as yaws rather than syphilis, a related treponemal infection. Gantenbein argues Hutten probably died of an acute illness such as pneumonia, not directly of the infection. Either way, the man who wrote the advertisement for the cure was not cured.

1520s to 1530s: money and dissent. Modern accounts often state that the Augsburg banking house of Fugger held a Spanish monopoly on guaiac in return for loans to the crown and ran "wood houses" for pox patients; Bičak repeats it. Claudia Stein's 2003 study of the French pox in Augsburg, however, titles its section on the subject "a legend that will not die," and what the Fuggers documentably founded were private pox hospitals in 1523/24 and 1572. Paracelsus attacked guaiac as useless in his Nuremberg syphilis writings of 1529. Girolamo Fracastoro's 1530 poem, which gave syphilis its name, praised the wood.

Price. In late 16th century Florence a single course could cost 2 to 13 percent of an unskilled construction worker's annual earnings, according to figures Bičak cites, and a 1992 CITES proposal reported prices of up to 7 gold crowns a pound around 1520 to 1530. Between 1568 and 1608 more than 21 tons reached Seville.

Why it seemed to work. Bičak notes that patients who switched from mercury improved partly because they had stopped taking mercury, whose effects included salivation, tremor, tooth loss and kidney damage. Add syphilis's habit of going quiet between stages, and a useless decoction could produce grateful testimonials. Its popularity faded by the second half of the 16th century, and mercury remained standard until arsphenamine (Salvarsan) and then penicillin. Sarsaparilla, another New World "blood purifier," followed a similar arc.

After syphilis: gout and rheumatism. Later pharmacopeias moved guaiac to joint disease. The 1911 codex said that in chronic rheumatism and gout it "may relieve pain and inflammation," and that taken between attacks it might reduce recurrence. That is the claim homeopathic labels carry today, still without a human trial behind it.

Potential Negatives & Side Effects

Diarrhea and gut irritation. The best-documented effect, and dose-related. In the human feeding work JECFA summarized (Johnson and colleagues, 1958), six people took a total of 10 doses of 2 or 3 grams of resin, and the only effect reported was one or two loose stools in some instances. Herbal references cited in the 2025 Turkish opinion list diarrhea, gastroenteritis and intestinal cramps at high resin intake, and nausea, gastroenteritis and diarrhea at high wood intake.

Skin reactions. Rashes appear in the same herbal references. The one primary dermatology report I found is occupational: hand dermatitis from guaiac in a printing paste (Sugai and Okuno, 1980).

Palpitations, dizziness and drowsiness. Listed for high doses of the wood in a draft German plant list (BVL, 2010) cited by the Turkish opinion. I found no case report that measured any of these.

A poisoning report from India. Bhushan and Agarwal (Journal of the Association of Physicians of India, 2019) described guaiacum toxicity in the setting of substance abuse of a homeopathic guaiacum product, warning that excess intake "may be life threatening and can damage the vision permanently." The abstract does not state the preparation, its alcohol content, the amount taken or the mechanism, and I could not obtain the full text.

Confusion with other products. A buyer looking for guaiac wood may receive Bulnesia wood or oil, and a buyer looking for an expectorant may confuse guaiacum with guaifenesin. Each substitution changes what is actually swallowed.

Displacement of real treatment. For syphilis this is the historical harm. For rheumatoid arthritis and gout the modern version is the months of joint damage or repeated attacks that accrue while an unproven remedy is tried first.

Deficiency Symptoms

What guaiacum addresses

No deficiency state exists. No human enzyme, tissue or pathway requires a guaiacum lignan, and no symptom arises from never encountering one. Gout and rheumatoid arthritis, the conditions it is sold against, have identifiable causes, and neither is a shortage of resin.

Bottom line

Nothing to replace, nothing to measure, and no reason to take it for "support."

Toxicity Symptoms

At high intake

• Loose stools at single doses of 2 to 3 grams of resin in the small human series JECFA reviewed.

• Diarrhea, gastroenteritis and intestinal cramps at high resin intake, per herbal references.

• Nausea, palpitations, dizziness and drowsiness at high wood intake, per a German draft list.

• Acute oral toxicity in animals is low but not uniform: JECFA recorded oral LD50 values above 5,000 milligrams per kilogram in rats and above 2,000 in mice, but 1,120 milligrams per kilogram in guinea pigs.

• For the bark, one mouse in the 1,000 milligrams per kilogram group died within 24 hours in the Williams study of an aqueous extract; none died at 125 or 300.

• In a Puerto Rican screen of seven plants, chloroform and ethyl acetate extracts of G. officinale were the most lethal to brine shrimp, with LC50 values below 10 micrograms per milliliter (Claudio-Campos and colleagues, Puerto Rico Health Sciences Journal, 2015). That is a crude cytotoxicity signal, not a human dose.

Signs to reduce or stop

Stop on diarrhea that persists beyond a day, abdominal cramping, a rash or itching, palpitations, dizziness or any change in vision. Any change in vision after taking a guaiacum product, especially a liquid one, needs emergency assessment, and the bottle should go with the patient.

General note

The long-term data are thin but not absent. JECFA reported that 11 people (four women, seven men) given 50 or 100 milligrams of resin daily for 18 to 104 weeks showed no change in blood counts, hemoglobin, kidney function, body weight, stool pattern or general condition. In animals, rats fed diets of up to 0.5 percent resin over their lifetime and into a third generation showed no differences in growth, lifespan, reproduction or pathology, and the no-effect level was set at 250 milligrams per kilogram of body weight. The 2025 Turkish opinion reported that it found no genotoxicity studies. JECFA also cited a 1938 finding that very little resin is absorbed: much passes out in the feces and the rest is broken down in the colon. Low absorption fits the clean food-additive record, and it is also a reason to doubt that swallowed resin reaches a joint in active form.

How Guaiacum Works

No mechanism has been shown for any therapeutic effect in people. What is established is the chemistry of the color test, plus a handful of cell and animal observations.

The color reaction. Heme, the iron-containing part of hemoglobin, has peroxidase-like activity. On a guaiac card, the developer supplies hydrogen peroxide (under 4.2 percent in the Hemoccult SENSA developer, in 80 percent denatured alcohol), and heme speeds the oxidation of alpha-guaiaconic acid to a blue quinone compound. Any other oxidant or peroxidase can do the same thing: the 1911 codex listed ferric chloride, ozone, hydrogen peroxide and chromic acid as turning the resin "guaiac-blue," and plant peroxidases in raw fruit and vegetables do it too. The effect of horseradish peroxidase on guaiacum was noted as early as 1810. That is why the test needs dietary rules and why it detects blood without identifying it as human.

Antioxidant activity. The same readiness to be oxidized is what lets the phenolic lignans of the resin protect the fats they are dissolved in, which is its food-additive function.

Nitric oxide suppression in liver cells. Nakano and colleagues (2016) purified six lignans from commercial guaiac resin and found that all six significantly reduced nitric oxide production in rat hepatocytes stimulated with the inflammatory cytokine interleukin-1 beta. This is a standard screening model for anti-inflammatory compounds, run in a dish.

Arachidonic acid and blood vessel growth. Ito and colleagues (International Journal of Cancer, 1993) tested alpha-guaiaconic acid, coded GR-12, and 20 synthetic derivatives. GR-12 inhibited arachidonic acid metabolism, and GR-12 and one derivative inhibited tube formation by human microvascular endothelial cells. In a mouse model of tumor angiogenesis, the derivative GS-01 inhibited new vessel growth; alpha-guaiaconic acid itself did not.

Saponins. The bark, leaves and flowers carry triterpenoid saponins (Section 1), which are surface-active and a plausible source of gut irritation from wood or bark preparations. The resin lignans, not the saponins, are what the color test and food uses depend on.

Why rat results do not transfer. The positive rat paw studies used extracts at 200 milligrams per kilogram by mouth, or bark extract at 16 to 32 milligrams per kilogram with an uncertain route. JECFA's human data point to poor absorption of the resin. I found no human pharmacokinetic study measuring any guaiacum lignan in blood after any dose.

Synergistic Supplements

None demonstrated. The only tested combination is topical: the G. officinale plus Rhodomyrtus tomentosa acne cream, where the authors report that a 1:1 mix suppressed inflammatory signals in skin cells 2.3 to 7.9 times more strongly than the guaiacum extract alone. That is a cell-culture comparison, and the human arm had no control group. Historical pairings, such as resin with rhubarb, sulfur and cream of tartar in the codex's compound confection for gout, are pharmacy history.

Interactions & What NOT to Take

Before a guaiac stool test. This is the interaction that affects the most people, and it runs from supplements and food to the test. The Hemoccult SENSA instructions say:

• Avoid more than 250 milligrams a day of vitamin C from supplements, and citrus fruits and juices, for 3 days before and during collection. Vitamin C can cause false negatives.

• Avoid red meat (beef, lamb and liver) for 3 days before and during collection, because animal heme can cause false positives.

• Avoid aspirin above 325 milligrams a day and other nonsteroidal anti-inflammatory drugs for 7 days before and during collection, because they can cause minor gut bleeding that yields a positive. Acetaminophen is acceptable.

• Iron supplements do not cause false positives, but an iron product containing more than 250 milligrams of vitamin C can cause a false negative.

• Raw fruits and vegetables carry plant peroxidases that can cause false positives if a slide is developed immediately; waiting at least 3 days lets them degrade.

The insert also lists alcohol in excess, corticosteroids, anticoagulants, some chemotherapy drugs and iodine-based antiseptics as causes of false positives. Blebea and colleagues (Archives of Pathology and Laboratory Medicine, 1985) found that as little as 0.005 milliliters of a 1:1,000 dilution of povidone-iodine turned a guaiac slide positive, probably by oxidizing alpha-guaiaconic acid directly.

Lithium. Rated a moderate interaction by Natural Medicines (as reproduced on WebMD), on theoretical grounds (Section 7). I found no case report or pharmacokinetic study that supports or refutes it.

Guaifenesin. Not an interaction, a mix-up. Guaifenesin is a synthetic cough expectorant derived from guaiacol, and taking a guaiac resin product does not substitute for it or add to it.

Drug-metabolizing enzymes. I found no study of guaiacum against any cytochrome P450 enzyme or drug transporter, and no case report of an interaction with a named drug.

What not to take. Any guaiacum product as a treatment for a possible sexually transmitted infection. Any unidentified wood chips sold as "lignum vitae," which may be Bulnesia or another hardwood. Any homeopathic Guaiacum at 1X or other low potency in pregnancy, while breastfeeding or for a child, given the absence of data.

Quality, Testing & Adulteration

Adulteration is as old as the trade. Sixteenth century dealers hid damaged wood under clay and cut guaiac shavings with cheaper wood, according to a history published by Métode, the University of Valencia's science magazine. The economics have not changed: a dense, dark, resinous heartwood is hard to tell from other dense, dark, resinous heartwoods once it has been chipped.

The trade names overlap. Argentina's 2010 CITES proposal for Bulnesia sarmientoi listed its trade names as "vera, verawood, lignum vitae, Paraguay lignum vitae, Argentine lignum vitae, guaiac." The US flavoring regulation groups G. officinale, G. sanctum and Bulnesia sarmientoi under the single common name "Guaiac." A product labeled "lignum vitae" or "guaiac" therefore does not tell you which genus is inside.

Species mislabeling inside the genus. The 2002 CITES proposal described a Canadian import of 1,450 kilograms of G. coulteri in 2000 that was declared as G. sanctum. It also noted that German resin and chip imports estimated at 20 to 40 tonnes a year did not match the tiny amounts reported, a gap it attributed to unreported imports, misdeclaration or other factors. Diagnostic resin is not necessarily from the two "official" species either: the same proposal reported US imports of 1.5 tonne batches of resin from Mexico for test kits, and a later Plants Committee document describes the resin imported into the United States for diagnostic kits as G. coulteri.

Homeopathic product control. The Rxhomeo 1X tablet's DailyMed record shows all its NDC codes inactivated under an FDA-initiated compliance action. The record does not say what the problem was.

Third-party testing. I found no USP, NSF or ConsumerLab program covering guaiacum products. Diagnostic cards are the guaiacum-containing products with the clearest published quality control: the Hemoccult SENSA insert reports 96.5 percent specificity in asymptomatic people on a restricted diet and built-in performance monitors that must react correctly for a result to count.

What paperwork a serious supplier can produce. For bulk wood or resin crossing a border: a CITES export permit, because annotation #2 covers raw resin, chips and extracts. For identity: the species and the plant part, beyond the bare word "guaiac." For resin purity: alcohol-insoluble matter and ash, judged against the old codex limits of under 8 and under 3 percent for block resin. For food-grade resin: conformity with the JECFA specification. For homeopathic products: the stock (resin) and potency on the label, which US labels already show.

A test you can run at home. Guaiaconic acid turns blue when oxidized, and peroxidase speeds that up. Dissolve a pinch of resin, or a few drops of an alcohol tincture, in a spoonful of high-proof spirit, add a few drops of 3 percent drugstore hydrogen peroxide, and touch it with a freshly cut slice of raw horseradish. A rapid blue means guaiaconic-type lignans are present. It does not prove species, and a 30C homeopathic pellet will not react because there is nothing left to oxidize.

Special Considerations

The CITES history, in order. G. sanctum timber entered Appendix II with the Convention's entry into force on July 1, 1975, and most parts and derivatives were regulated from 1985. In 2000 the United States proposed moving G. sanctum to Appendix I; it remained in Appendix II. G. officinale followed on June 11, 1992, on a US proposal. In 2002 Germany, on behalf of the European Community, proposed listing every Guaiacum species under Article II, paragraph 2(b), the look-alike provision, because the woods could not be told apart in trade; that listing took effect on February 13, 2003.

What the annotation covers. A 2006 CITES Plants Committee document noted that under the annotation then in force, resin and oil were exempt from controls but "should be covered by controls," a gap the current annotation closes. The current annotation #2 covers "All parts and derivatives except: a) seeds and pollen; and b) finished products packaged and ready for retail trade." In international trade, raw resin, chips and bulk extract need permits; a retail-packaged bottle or tube does not.

Conservation status. On the IUCN Red List, G. officinale is assessed as Endangered (2019) and G. sanctum as Near Threatened (2017). NatureServe ranks Florida's G. sanctum, confined to the Keys and Miami-Dade County, as critically imperiled. As of the 2002 proposal, Mexico placed G. sanctum and G. coulteri under special protection, and Mexican exports of G. sanctum fell after a policy change in 2001. In Oaxaca, Gordon and colleagues (Oryx, 2005) surveyed 18 dry forest patches and found G. coulteri absent from 13; all 42 individuals they did find were shrubs, none over 25 centimeters in trunk diameter, in a district where informants remembered trees over 100 centimeters felled for export in the late 1950s.

Where the demand actually is. The 2002 proposal found only one shipment in 20 years entering international medicinal trade, and described local and national medicinal markets as nearly nonexistent. The demand today is timber, liqueur flavoring and diagnostic resin, not supplements. That contrasts with the more than 21 tons of guaiac that reached Seville between 1568 and 1608, when the wood was the medicine.

Guaiac versus immunochemical stool tests. Guaiac cards are being displaced in screening. A 2020 meta-analysis of 31 studies in Anticancer Research found an area under the curve of 0.77 for guaiac tests against 0.87 for immunochemical tests (P = 0.0017), and its authors recommended immunochemical tests for new screening programs. Immunochemical tests detect human hemoglobin with antibodies, so they do not need the meat and vegetable restrictions.

Pregnancy, breastfeeding and children. No data for any form (Section 7).

Research Status & Evidence Quality

Tier 1, randomized human evidence for oral guaiacum. None found. PubMed searches combining guaiacum, guaiac resin, lignum vitae and the species names with trial or randomized terms returned stool-test studies, case reports mentioning "guaiac-positive" stool, and history papers, but no trial of the herb.

Tier 2, other human data. JECFA's safety series (six people at 2 to 3 gram doses; 11 people at 50 to 100 milligrams daily for up to 104 weeks), which measured tolerance, not benefit. One uncontrolled 28-day topical study in 30 adults of a two-plant acne cream (Zhang, 2024). One case report abstract of homeopathic guaiacum toxicity (Bhushan, 2019).

Tier 3, animal and laboratory work. Rat inflammation models (Duwiejua, 1994; Williams, 2017; Sarkar, 2014, homeopathic); rabbit and rat glucose studies, two of them on G. coulteri (Román Ramos, 1992; Ibrahim, 2019); antimicrobial screens of G. coulteri; lignan chemistry and nitric oxide assays (Nakano, 2016); endothelial cell work on alpha-guaiaconic acid (Ito, 1993).

Tier 4, tradition and history. Syphilis, from 1508 through the 16th century; gout, rheumatism and tonsillitis in pharmacopeias into the 20th century; German monograph use for rheumatic complaints.

Separate and strong: the reagent. Guaiac-based stool testing has randomized mortality data in tens of thousands of people (Mandel, 1993 and 1999), and is now being superseded by a better test.

Research Limitations

No human pharmacokinetic study of any guaiacum lignan exists that I could find, so nobody knows what blood level, if any, follows a cup of guaiac wood tea or a gram of resin. Animal studies used undefined extracts without marker quantification, at doses per kilogram far above JECFA's human ceiling. Three species (G. officinale, G. sanctum and G. coulteri) appear across the literature and the trade, and evidence from one is easily read as applying to the others. The Bhushan poisoning abstract lacks the details needed to judge cause. The German reference figure of 4.5 grams of wood a day comes from a secondary source, the Altmeyers encyclopedia, and I could not retrieve a primary monograph text for it.

Summary & Key Takeaways

Bottom Line

Guaiacum was one of the first New World drugs sold across Europe, arriving in Spain by 1508 as a cure for the French pox and championed in print by a patient who relapsed and died four years after his book appeared. It never cured syphilis, and no human trial has shown it treats gout, rheumatism or anything else when swallowed. What survives is chemistry: its resin is a food antioxidant with a JECFA ceiling of 2.5 milligrams per kilogram a day, and its alpha-guaiaconic acid is the blue in the guaiac stool test. The trees themselves are now protected under CITES, with G. officinale assessed as Endangered.

Key Safety Points

• Possible syphilis needs a blood test and penicillin, never a herbal or homeopathic remedy.

• High resin intake causes diarrhea and gut cramping; skin contact can cause dermatitis.

• Avoid in pregnancy, breastfeeding and childhood; there are no safety data, and the resin was historically used to bring on menstruation and, reportedly, abortion.

• Before a guaiac stool test, follow the vitamin C, red meat, aspirin and NSAID restrictions, or the result may be wrong.

• "Guaiac," "lignum vitae" and "palo santo" can each mean Bulnesia; guaifenesin is a different, synthetic compound.

Special Note

Guaiac's appeal in 1519 was that it was gentler than mercury, and on that narrow point it delivered: no salivation, no loosened teeth, no tremor. That is a low bar, and it is the only one guaiacum ever cleared as a medicine. Its lasting contribution came four centuries later, when a peroxidase reaction on a paper card helped show, in a randomized trial of 46,551 people, that screening for hidden blood cuts colorectal cancer deaths.

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Researched and drafted with AI assistance. Every claim verified against primary sources and human-reviewed before publication. Last reviewed: November 2, 2026. Corrections: reply to any issue.

This issue is for education and is not medical advice. If you take prescription medication or live with a diagnosed condition, talk with your clinician before you start, stop or change anything you take.