Guaiac

Botanical

What is it

Guaiac (Guaiacum officinale, Guaiacum sanctum) is a tropical American tree. Its wood and resin (called gum guaiac) have been used historically for rheumatism, gout, and skin conditions, and as a chemical reagent for fecal occult blood tests in clinical laboratories.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Reagent use (fecal occult blood)

Strong Evidence

Guaiac paper is a standard reagent in screening tests for fecal occult blood (used in laboratory diagnostics, not as a supplement benefit).

Joint discomfort and gout (traditional)

Mixed Evidence

Used in 18th and 19th century medicine for rheumatism. No modern clinical evidence supports these uses.

How it works

Guaiac wood and resin contain lignans (guaiaretic acid, alpha- and beta-guaiaconic acid) and resinous compounds. Traditional uses focused on diaphoresis (sweating) and anti-inflammatory effects. Modern use as a dietary supplement is uncommon; the most familiar medical use is as a reagent in fecal occult blood tests, where the guaiac compound is oxidized to a blue color by peroxidase-like activity of heme in blood.

Dosage

No standardized supplement dose. Traditional doses used grams of resin per day, with significant side effects.

When and how to take it

No evidence-based timing. Should be discontinued before fecal occult blood screening tests.

1 commercial form

Compare the main delivery options and what they’re best suited for.

Gum guaiac resin

Historic use as a tincture or powder.

Variable; traditional preparations.

Safety

Can cause GI upset, allergic contact dermatitis, and (rarely) renal effects at higher doses. Guaiacum extracts can affect the results of fecal occult blood tests. Guaiacum is a protected species under CITES due to overharvesting; sourcing should be ethical.

Who should be cautious

Avoid in pregnancy and breastfeeding. Avoid in people with active GI bleeding (interferes with stool tests). Use cautiously in people with kidney disease.

Interactions

Can interfere with fecal occult blood test results (false positives possible). Theoretical interactions with NSAIDs and other anti-inflammatory drugs based on tradition.

Frequently asked questions

Is guaiac the same as guaifenesin?⌄

No, but they share a name origin. Guaifenesin is a synthetic expectorant historically derived from guaiacol, a compound from guaiac wood; the two have different uses.

Is guaiac sustainable?⌄

Guaiacum species are CITES-listed due to overharvesting. Sourcing should be ethical.

References

Guaiac on Wikidata — Wikidata link

Guaiac on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Guaiac (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.