Guaiac

Other Names

Bois de gaiacBois de gayacBois de vieBuckwoodFranzosenholzFrenchwoodGaïacGaïac officinalGaïacwoodGayacGuaiac resinGuaiaci lignumGuaiaci resinaGuaiacoGuaiacumGuaiacum bijugumGuaiacum breyniiGuaiacum officinaleGuaiacwoodGuajacan negroGuajacoGuajacum officinaleGuajakbaumGuajakholzGuajakholzbaumGuayacánGuayacanGuayacán negroGum guaiacHoly woodLegno guajacoLegno santoLignum benedictumLignum guajaciLignum sanctumLignum vitaePalo santoPalosantoPalus sanctusPau santoPockenholtsPockholzPockwoodPokhoutResin guaiacRough bark lignum-vitaeRoughbark lignum-vitaeSchlangenholzTree of lifeUajacumWayacaWayaká

Synopsis

Guaiac (Guaiacum officinale & Guaiacum sanctum): A Comprehensive Reference

1. Identity and Botanical Classification

Species and Taxonomy

Guaiacum resin is obtained from the heartwood of Guaiacum officinale and G. sanctum (Zygophyllaceae), small evergreen trees found in the dry coastal regions of tropical America. Guaiacum officinale, commonly known as roughbark lignum-vitae, guaiacwood, or gaïacwood, is a species of tree in the caltrop family, Zygophyllaceae, that is native to the Caribbean and the northern coast of South America. Guaiacum officinale is found on the coast of Venezuela and Colombia and in the West Indies, while G. sanctum occurs in Cuba, Haiti, the Bahamas, and Florida. Little is now found in commerce.

This small tree is very slow-growing, reaching about 10 m (33 ft) in height with a trunk diameter of 60 cm (24 in), and is essentially evergreen throughout most of its native range. The blue flowers have five petals that yield a bright-yellow-orange fruit with red flesh and black seeds. Guaiacum officinale is the national flower of Jamaica. The genus is famous as the supplier of lignum vitae, ranked as the fourth-hardest variety of wood as measured by the Janka hardness test, requiring a force of 4,500 lbf (20,000 N) to embed a steel ball half its diameter into the wood.

The name Guaiacum derives from the Taíno word guayacán, reflecting its indigenous Caribbean roots, while officinale denotes its medicinal legacy. The plant is known by numerous synonyms and common names, including: Bois de Gaïac, Bois Saint, Bois de Vie, Gaïac, Guaiac, Guaiac Heartwood, Guaiac Resin, Guaiacum, Guaiacum guatemalense, Guajaci Lignum, Guayacán, Guayaco, Lignum Vitae, Palo de Hierro, and Pockwood.

Conservation Status

Guaiacum officinale (roughbark lignum-vitae) was listed as an endangered species by the IUCN in 2019. It has been overexploited for its valuable wood and medicinal products. Guaiacum deserves special handling in terms of conservation: Guaiacum officinale is slow-growing, heavily exploited in the past for both wood and resin, and now subject to trade controls.

Botanical Parts Used

The tree inhabits the West Indian Islands, especially Jamaica, St. Thomas, and St. Domingo. The wood and resin, or solidified juice, are the parts used in medicine, though the whole tree possesses medicinal virtues. The bark is said to be the most active part of it, but it is seldom met with in commerce.

Common Preparations and Dosage Forms

Bark and resin are available powdered, tinctured, and in the form of decoctions. The resin is procured from the wood of the tree by natural exudation; by wounding the tree in several places; by heat applied to the wood sawed into large billets; and by boiling the chips of the wood in water and salt and skimming off the resin as it floats on the surface. Guaiac wood, consisting of the heartwood and the sapwood, contains guaiac resin as the main active ingredient, stored in the wood in zones resembling irregular annual rings. The heartwood contains up to 25% resin whereas only 2 to 3% resin is present in the sapwood.

Guaiacum resin occurs in large blocks or rounded tears about 2–3 cm diameter. The freshly fractured surface is brown and glassy. The powder is greyish but becomes green on exposure to air. It has a somewhat acrid taste and an aromatic odour when warmed.

As a food additive, Guaiacum is designated E314 and classified as an antioxidant. In the food industry, guaiac resin is used as an antioxidant to preserve above all animal fats. A widely used derivative drug is the expectorant known as guaifenesin.

A Note on "Guaiac Wood Oil" (Oil of Guaiac)

Oil of guaiac is a fragrance ingredient used in soap and perfumery. Despite its name, it does not come from the Guaiacum tree, but from the palo santo tree (Bulnesia sarmientoi). Oil of guaiac is produced through steam distillation of a mixture of wood and sawdust from palo santo. Oil of guaiac is primarily composed of 42–72% guaiol, bulnesol, δ-bulnesene, β-bulnesene, α-guaiene, guaioxide, and β-patchoulene. This is chemically distinct from the resin of true Guaiacum species and should not be conflated with medicinal guaiacum preparations, though there is significant commercial confusion between the two.

2. Traditional and Historical Use

Indigenous Caribbean Use (Pre-Columbian Era)

The wood and resin of this tree was used as a medicine by the natives long previous to the discovery of the country, and they made it known to the Europeans; by these it was introduced into Europe in the sixteenth century, and employed to much advantage in syphilitic affections. The Taíno used it for arthritis, syphilis, and respiratory ailments, sharing it with Spanish explorers in the 16th century, who dubbed it a "miracle cure" for syphilis, leading to its widespread use in Europe.

European Use: 16th–19th Centuries

The resin, known as guaiacum resin, was introduced to Europe in the early 16th century by Spanish explorers and quickly gained popularity as a treatment for syphilis and other venereal diseases. In the 16th and 17th centuries, guaiacum resin was considered a valuable remedy in the treatment of gout, rheumatism, and various inflammatory conditions. It was believed to possess purifying properties, making it a popular choice for "cleansing the blood."

In the 19th century, eclectic physicians prescribed Guaiacum for rheumatism, gout, and skin diseases, valuing its alterative and diaphoretic properties. By the late 19th and early 20th centuries, it remained in old pharmacopoeias, though mostly as an empirical remedy rather than a fully proven medicine.

Over time, guaiac wood was also administered for the treatment of numerous other diseases, above all for rheumatic diseases, arthritis, asthma, tuberculosis, and malaria. Applications for the treatment of smallpox gave the tropical wood, among others, the popular name "pockwood."

Traditional Caribbean Folk Medicine (Continuing)

In Caribbean folk medicine, it remains a remedy for colds, joint pain, and ulcers, often brewed as a tea or applied as a poultice.

Eclectic and Specific Medical Uses

According to the eclectic medical tradition, the chief uses for guaiac were in rheumatic pharyngitis or rheumatic sore throat and incipient tonsillitis, with angry, red, raw-looking surfaces. The latter may be the type which is the forerunner of an attack of acute inflammatory rheumatism — the tonsils being the foci of infection. In such cases it was said to act better than in other forms of amygdalitis. While seemingly indicated in active conditions in sore throat and in chronic rheumatism, it was described as best adapted to passive conditions — cold hands and feet, feeble circulation, and vital depression.

Homeopathic Tradition

Guaiacum officinale was introduced into homeopathic medicine by Samuel Hahnemann, the founder of homeopathy. In homeopathy, the remedy is prepared by potentizing the resin, described as effective for treating a range of conditions related to inflammation, particularly those affecting the joints and fibrous tissues. The monograph for the Commission D in the German Federal Gazette (Bundesanzeiger, 1985) mentions tonsillitis, throat inflammations, inflammations of bronchi and lungs, rheumatism, and gout as applications in accordance with the homeopathic drug concept.

3. Key Constituents and Active Compounds

Resin Composition

Principal constituents of guaiac resin are three resins: guaiaconic acid (approximately 70%), guaiacic acid, and guaiaretic acid. Some of the main resinous constituents are lignans. These are phenolic compounds having a C18 structure formed from two C6–C3 units. Guaiaretic acid, which forms about 10% of guaiacum resin, is a diaryl butane. The flowers, fruit, and bark of the tree contain triterpenoid and nortriterpenoid saponins.

This resin is composed of various colophonic acids of the furoguaiacin type (α and β guaiaconic acid) and lignan type (guaiaretic acid and guaiacinic acid), as well as the phenol guaiacol. Other active ingredients of guaiac wood include essential oils (guaiac wood oil) which is mainly composed of the sesquiterpene alcohol guaiol, alkaloids, and triterpene saponins with the aglycone oleanolic acid.

Research has demonstrated the presence in the heartwood of Guaiacum officinale of at least nine lignans. In addition to guaiaretic acid and its dihydro-compound, dehydroguaiaretic acid and two tetrahydro-derivatives — guaiacin and isoguaiacin — have been found. The accompanying dimethoxydihydric phenol, furoguaiacin, and its monomethyl ether afford examples of the unusual furano-lignans. The occurrence of two optically inactive tetrahydrofurans, tetrahydrofuroguaiacin-A and -B, was also established.

The resin of guaiac, upon dry distillation, yields a brown-red tar containing guaiacol (C₇H₈O₂), pyroguaiacin, guaiol (guaiacen), and kreosol.

Characteristic Color Reaction (Diagnostic Basis)

Guaiac, a natural resin extracted from the wood, is a colorless compound that turns blue when placed in contact with substances that have peroxidase activity and then are exposed to hydrogen peroxide. Guaiac cards are impregnated with the resin and are used in determining whether stool contains blood. The heme portion of hemoglobin contains peroxidase and will catalyze the oxidation of guaiaconic acid when hydrogen peroxide is placed on the guaiac card if blood is present in the stool.

This detection of occult blood is based on the oxidation of α-guaiaconic acid to the quinoid guaiac blue (furoguaiacin blue). An alcoholic solution of guaiacum resin gives a deep blue colour (guaiac-blue) on the addition of oxidizing agents such as ferric chloride. This colour is destroyed by reducing agents.

Guaifenesin: A Notable Derivative

A widely used derivative drug is the expectorant known as guaifenesin. Guaifenesin (also spelled guaiphenesin) is a synthetic derivative of guaiacol — itself a breakdown product of guaiac resin — and is the active ingredient in many modern over-the-counter cough and cold preparations. It is important to note that guaifenesin is a distinct, fully synthetic pharmaceutical, not the resin itself.

4. Mechanisms of Action

Anti-inflammatory Mechanisms (Laboratory Evidence)

Modern laboratory work has identified lignans in guaiac resin and shown anti-inflammatory activity in cell-based models, including reduced nitric oxide production. Guaiac constituents have been attributed with antiseptic, anti-inflammatory, antimicrobial, antioxidant, epithelializing, antimutagenic, immunomodulatory, fungicidal, expectorant, diuretic, diaphoretic, demulcent, and bitter stimulant properties.

Guaiac resin constituents are potent antioxidants that can scavenge hydroxyl radicals and inhibit lipid peroxidation in rat hepatic microsomal membranes (in vitro). Whereas the ingredients of guaiac resin have a diuretic and diaphoretic effect, the fungicidal action of an extract of guaiac wood is attributed to the saponins contained in the wood.

Phosphodiesterase-4 (PDE4) Inhibition

Scientific patent literature has described the use of extracts or extract substances from Guajacum species wherein said extracts effect a phosphodiesterase-4 inhibition. PDE4 inhibition is recognized as an anti-inflammatory mechanism relevant to rheumatic and airway inflammatory conditions, providing a molecular basis for some of the traditional uses of the plant, though this mechanism has not been validated in clinical trials specific to guaiacum.

Nordihydroguaiaretic Acid (NDGA): A Structurally Related Lignan

Note: NDGA is a lignan structurally related to those found in guaiacum resin but is primarily sourced from the unrelated creosote bush (Larrea tridentata). It has been studied extensively in isolation and provides a pharmacological model for understanding how guaiac-type lignans may act; however, findings on NDGA cannot be directly extrapolated to guaiacum preparations without further investigation.

NDGA presents two catechol rings that confer a very potent antioxidant activity by scavenging oxygen free radicals, and this may explain part of its therapeutic action. Additional effects include inhibition of lipoxygenases (LOXs) and activation of signaling pathways that impinge on the transcription factor Nuclear Factor Erythroid 2-related Factor (NRF2). More specifically, NDGA is a potent lipoxygenase inhibitor which interferes with arachidonic acid metabolism. The compound also inhibits formyltetrahydrofolate synthetase and carboxylesterase, and, to a lesser extent, cyclooxygenase.

5. Scientific Evidence by Area of Use

5.1 Fecal Occult Blood Testing (Diagnostic Use — Strongest Evidence)

Guaiac is a natural resin extracted from specific tree species, notably Guaiacum officinale and Guaiacum sanctum. Its most prominent modern medical application is in the guaiac-based fecal occult blood test (gFOBT) for detecting hidden blood in stool.

Evidence from Randomized Controlled Trials: Guaiac-based FOBTs are the only stool tests for which there is evidence of efficacy in terms of CRC-related mortality reduction from prospective, randomized controlled trials (RCTs). These trials from the USA, United Kingdom, Denmark, and Sweden demonstrated that multiple rounds of annual or biennial gFOBT screening can reduce CRC-related mortality. Two RCTs from the United Kingdom and Denmark showed significant reduction in CRC mortality using unrehydrated gFOBT biennially, with relative risk reductions of 13% (UK trial) and 16% (Danish trial); absolute differences of 0.1% (UK trial) and 0.2% (Danish trial). No significant reduction in overall mortality was observed. Unrehydrated gFOBT had low sensitivity for CRC detection (45% in the UK trial and 54% in the Danish trial).

A meta-analysis pooled data from RCTs and found a CRC-specific mortality rate ratio of 0.88 (95% CI: 0.80–0.96) for guaiac-based fecal occult blood test screening.

Sensitivity and Specificity: For the detection of CRC, the summary sensitivity of gFOBTs was 39% (95% CI 25% to 55%), which was significantly lower than FITs. No significant differences in summary specificity for advanced neoplasia detection were found between gFOBTs (94%; 95% CI 92% to 96%) and FITs.

The sensitivity and specificity of gFOBT screening varies widely due to variation in type of test (brand), instructions for stool collection, number of stool samples per screening round, the use of non-hydrated or rehydrated stool samples, double reading of the test, the number of positive panels used to refer a screened person for colonoscopy, and the interval between successive screening rounds.

Comparison with newer FIT tests: Specificity of both gFOBT and FIT tests was similar in studies using all subjects as the reference standard, whereas specificity was significantly higher for gFOBTs than FITs in studies using only test-positive subjects as the reference standard. However, at pre-specified specificities, the sensitivity of FITs was significantly higher than gFOBTs. FITs have several advantages over guaiac-based FOBTs, including higher sensitivity and specificity, resulting in improved clinical performance and higher efficiency.

However, gFOBT has significant limitations. This form of screening is associated with a substantial interval cancer rate in the region of 50%, indicating a severe deficiency in sensitivity for cancer. Furthermore, as the majority of colorectal cancers arise from pre-existing adenomas, detecting adenomas is important for any colorectal screening programme to reduce the incidence of the disease.

Evidence Strength: HIGH (for diagnostic/screening use only, supported by multiple large RCTs and systematic reviews).

5.2 Rheumatic Conditions (Therapeutic Use — Weak/Preliminary Evidence)

Guaiacum resin, included in the British Herbal Pharmacopoeia (BHP, Vol. 1, 1990), is indicated for the treatment of chronic rheumatic conditions. Guaiacum resin included in the BHP (Vol. 1, 1990) is indicated for the treatment of chronic rheumatic conditions. It is a permitted food additive in the USA and in Europe.

People use guaiac wood and resin for conditions such as muscle and joint pain and for preventing gout, but there is no good scientific evidence to support these uses. Although application of guaiac wood or of guaiac resin has been described in connection with numerous medical indications, particularly as part of a homeopathic treatment of rheumatic diseases, there are no well-controlled studies in this area.

Animal studies have explored anti-rheumatic effects. Body weight, ankle and knee diameter, urinary parameters, serum interleukins including IL-1β, CINC-1, PGE2, TNF-α, IL-6, and IL-12 levels were significantly affected in a rat model of induced arthritis; after treatment with guaiacum in all three regimes, normalization of these parameters was observed compared to the control group. These are animal studies and do not constitute human clinical evidence.

Evidence Strength: WEAK — supported by pharmacopoeial listing and traditional use, but lacking robust human clinical trials. Current evidence is primarily animal-based and in vitro.

5.3 Gout Prevention and Uric Acid Excretion

Guaiacum is described in herbal traditions as useful in the treatment of gout and as a preventative, said to promote excretion of uric acid. In older herbal medicine, guaiacum was used for chronic rheumatic pain, gout, stubborn sore throats, skin complaints, and as a warming "blood-purifying" remedy. No controlled human clinical trials confirming these effects have been identified in the peer-reviewed literature.

Evidence Strength: VERY WEAK — based entirely on traditional use; no clinical trial evidence found.

5.4 Respiratory Conditions

Powdered extract of the plant is described in traditional medicine as useful in treating tonsillitis, while strong actions on the respiratory tract have not been noted. Guaiac resin's structural relationship to guaiacol, and through it to guaifenesin (an established expectorant), has led to speculation about expectorant properties, but guaiacum resin itself has not been validated as an expectorant in clinical trials.

Evidence Strength: VERY WEAK — traditional attribution only; no clinical evidence from human trials.

5.5 Syphilis (Historical Use — Obsolete)

Guaiacum also became famous in Europe as an early treatment for syphilis, though that use now belongs to medical history rather than modern care. Guaiac was also employed in chronic sore throat of syphilitic origin. This use has no relevance to contemporary medicine and is noted here for historical completeness only.

5.6 Antioxidant Activity

The resin contains lignans and resin acids that show anti-inflammatory and antioxidant activity in laboratory studies. It is a potent antioxidant that can scavenge hydroxyl radicals and inhibit lipid peroxidation in rat hepatic microsomal membranes. These findings are in vitro (cell culture and animal models) and have not been confirmed in human trials.

Evidence Strength: PRELIMINARY — in vitro and animal model data only.

6. Body Systems and Health Domains

Based on documented traditional use and laboratory research, guaiacum has been associated with the following body systems and health domains:

Musculoskeletal system: Used in chronic rheumatism and rheumatoid arthritis, particularly when an astringent is needed. It is also said to aid in the treatment of gout and may be used as a preventative.
Lymphatic/circulatory system: Traditional materia medica described guaiacum preparations as acting like stimulants, increasing the heat of the body and accelerating the circulation.
Gastrointestinal system: Large doses act as a cathartic. For digestive disorders, guaiacum has been used as a laxative.
Urinary system: For urinary tract conditions, guaiacum has been used as a diuretic.
Integumentary system: Guaiac oil has attributed anti-inflammatory, antiseptic, and wound healing-promoting properties.
Respiratory system: Traditional eclectic literature describes applications for tonsillitis and pharyngitis. The Commission D monograph mentioned tonsillitis, throat inflammations, and inflammations of bronchi and lungs as homeopathic indications.
Diagnostic/laboratory medicine: An alcoholic solution is used for the detection of blood stains, cyanogenetic glycosides, oxidase, and peroxidase enzymes.

7. Dosage Forms and Reported Dosages

Dosage information in the following section is drawn from historical pharmacopoeias, eclectic medical literature, and naturopathic reference sources. No standardized therapeutic dose has been validated in modern clinical trials.

Historical Pharmacopoeial Dosages

Of the wood: 30 to 60 grains; decoction: 2 oz. to 4 oz. in a pint of water; fluid extract: ½ to 1 drachm.
Guaiacum tincture (B.P. and U.S.P.): ½ to 1 drachm; ammoniated tincture of guaiacum (B.P. and U.S.P.): ½ to 1 drachm.
Guaiac resin: dose of 5 to 15 grains.
Specific Medicine Guaiacum: dose 5 to 30 drops.
Guaiacum wood: 30 to 60 grains (2.0–3.9 g).

Naturopathic Reference Dosages

Decoction: ¼ tsp per cup, simmered 20 minutes, ½ cup three times daily (TID).
Tincture (1:5, 90% ethanol): 1–4 ml TID. Friction rub: tincture applied over rheumatic area. Dried wood: 1–2 g TID.

Traditional Decoction

A traditional decoction often uses about 1–2 tsp dried plant material in 240 mL water, but no standardized modern oral dose is established.

8. Safety Considerations and Known Interactions

General Safety Profile

When taken by mouth, guaiac wood and guaiac resin are used as flavorings in food, but there is not enough reliable information to know if higher doses are safe. Higher doses have been reported to cause some side effects, including diarrhea and stomach and intestinal problems. Guaiac wood and guaiac resin can also cause skin rashes.

The resin's phenolics can irritate mucous membranes, and topical products may sensitize the skin in those prone to dermatitis. Most reactions occur early and improve after stopping the product.

Documented Adverse Effects

Gastrointestinal: upset stomach, cramping, loose stools, and nausea. Skin reactions: redness, itching, or rash with topical use. Headache or lightheadedness (generally mild and transient). Allergy: hives, swelling, or breathing difficulty may occur in rare cases.

Toxicity

Toxicity of guaiacum preparations can cause restlessness, forgetfulness, dilated pupils, diminution of vision, constipation, and headache. Its long-term effects are not well documented. A published case report highlighted that overuse of homeopathic guaiacum preparations may lead to life-threatening situations and permanent blindness if taken in excess. In the described case, a 40-year-old male patient presented with sudden diminution of vision and increased respiratory rate after alleged ingestion of approximately 200 mL of homeopathic Guaiacum 30; investigations showed severe metabolic acidosis.

From a mechanistic perspective relevant to closely related lignan compounds, the oxidation of the catechols to the corresponding quinones may elicit alterations in proteins and DNA that raise safety concerns.

Uterine Stimulant / Abortifacient Risk

Guaiacum has been identified as a uterine stimulant and used historically as an abortifacient. Avoidance of internal use during pregnancy, breastfeeding, and childhood is indicated. This represents a significant safety consideration for women of reproductive age.

Gastrointestinal Contraindications

In general plethora or inflammation of the gastro-enteric tract, guaiac is usually contraindicated.

Drug Interactions

Guaiacum officinale may interact with certain pharmaceuticals, potentially altering their effectiveness or increasing the risk of side effects. There are indications of concern regarding combination with anticoagulants or antiplatelet drugs due to possible increased bleeding risk. No formal pharmacokinetic drug interaction studies in humans have been published. The evidence base for claimed interactions is absent from the peer-reviewed literature for guaiacum specifically; these concerns are inferred from constituent chemistry.

Individuals with kidney, liver, or bleeding disorders should exercise particular caution and seek individualized guidance.

Food Additive Safety

Guaiacum resin is a permitted food additive in the USA and in Europe. This regulatory acceptance refers specifically to its use as an antioxidant preservative at food-grade concentrations, and does not constitute endorsement of therapeutic use at higher doses.

9. Regulatory and Pharmacopoeial Status

Guaiacum resin is included in the British Herbal Pharmacopoeia (BHP, Vol. 1, 1990), where it is indicated for the treatment of chronic rheumatic conditions. In historical U.S. and British pharmacopoeias, guaiacum was listed as "the resin of the wood of Guaiacum officinale Linné, or of Guaiacum sanctum Linné (Fam. Zygophyllaceae)." Today, guaiacum is a niche remedy in herbalism, used in anti-rheumatic blends and respiratory tonics, though its endangered status underscores the need for sustainable practices.

10. Summary of Evidence Strength

Fecal occult blood testing (diagnostic reagent): High-quality evidence from multiple large RCTs demonstrating a reduction in colorectal cancer–specific mortality of approximately 12–16% with biennial screening; the gFOBT's specificity is high (~94%), but sensitivity for CRC is limited (~39%). FIT-based tests now demonstrate superior sensitivity.
Rheumatic disease / joint pain: Pharmacopoeial listing (BHP 1990); animal model data suggesting anti-inflammatory mechanisms; no robust human clinical trial evidence.
Gout / uric acid: Traditional and historical attribution only; no clinical evidence.
Respiratory conditions / tonsillitis: Historical and traditional use; no clinical evidence.
Antioxidant activity: In vitro and animal model data; not confirmed in human clinical trials.
Syphilis: Historical use; entirely obsolete in modern medicine.

References

Health Conditions

Health conditions that Guaiac may help support.

No conditions available.

Body Systems

Body systems that Guaiac may help support.

No body systems available.