Lomatium

Lomatium (Lomatium dissectum)

1. Identity and Botanical Description

Accepted scientific name: Lomatium dissectum (Nutt.) Mathias & Constance. The botanical name was changed in 1942 by Matthias and Constance, from Leptotaenia dissecta to Lomatium dissectum. The plant is also documented under its prior synonym Leptotaenia dissecta Nutt. in earlier botanical and pharmacological literature.

Common names: Fernleaf biscuitroot; known as Toza by the Numic-speaking tribes. Lomatium is also known as Indian biscuit root, biscuit root, desert parsley, desert parsnip, fern-leafed lomatium, Indian desert parsnip, Indian parsnip, tohza, toza, and wild carrot.

Taxonomy and family: The name "lomatium" generally refers to Lomatium dissectum, one of the numerous species and varieties of the Lomatium genus that is native to western North America. Lomatium is a member of the Apiaceae (carrot) family and grows in the northwestern United States and southwestern Canada. The genus Lomatium comprises 98 species, widely distributed in western North America.

Morphology and habitat: This herb is a taprooted perennial extending approximately 30 cm long and 5 cm thick, with a thick stem that is finely ribbed and hollow. It is the largest member of the Lomatium genus, growing up to 1.3 m. It produces purple, maroon, or yellow flowers as well as oblong fruit that grows directly from the stem. Its habitat consists of dry, open, rocky slopes, grassy bluffs, and vernal meadows at low and middle elevations; it cannot grow in shade. Fernleaf biscuitroot naturally occurs from British Columbia and Saskatchewan south to California and New Mexico and extends eastward to Wyoming and Colorado.

Part used: The most commonly used type of desert parsley is Lomatium dissectum (fernleaf biscuitroot). The roots of this plant are used to make medicine. For cultivation as an herbal remedy, lomatium roots are unearthed during the months between early spring and fall. Roots are washed and dried for several days, then sliced and allowed to dry again.

Related medicinal species: While Lomatium dissectum is the most widely recognized and used species, it is not the only useful species of Lomatium. The entire genus consists of about 100 recognized species according to Plants of the World Online. All species are reported to be edible, and quite a few have been used as medicine, including L. ambiguum, L. californicum, L. canbyi, L. cous, L. foeniculaceum, L. graveolens, L. microcarpum, L. nudicaule, L. orientale, L. triternatum, and L. utriculatum. Because L. dissectum has one of the largest ranges of any Lomatium in the United States, it is the most widely used Lomatium species in herbal medicine. Of the 70 to 80 Lomatium species from western North America, only 20 occur in the ethnobotanical literature (Moerman, 2012).

Conservation status: Like many wild plants that have attracted the attention of commercial interests, lomatium is presently threatened with extinction over parts of its range.

2. Common Forms and Preparations

Lomatium is commercially available in several preparation forms:

• Tincture (full resin): Lomatium tincture, 1–3 ml three times per day, can be used, but it may cause a rash in susceptible people.
• Resin-free isolate (lomatium isolate): Lomatium extracts with the resins removed (often called lomatium isolates), 1–3 ml per day, have been recommended. These preparations were developed specifically to reduce the risk of the characteristic rash reaction associated with the resin fraction.
• Dried root and decoctions: Ethnobotanical records indicate that various indigenous peoples used the root as a decoction or tincture for "colds," "fevers," and respiratory complaints.
• Capsules and standardized extracts: The plant is also sold in encapsulated powdered-root form and as standardized extracts, though no standard dosage has been validated in controlled clinical trials.

When dried correctly, lomatium is said to keep its medicinal properties for 2–3 years.

3. Traditional and Historical Use

Indigenous North American Use

The root of Lomatium dissectum is considered to be one of the most commonly used plants in Native American society, dating back centuries. It served as a general remedy for common ailments, but was used most frequently to aid in the healing of small wounds and to cure respiratory issues. This plant is one of the most widely used plants in native North American culture, employed for food, medicine, and ceremonial purposes.

Tribes such as the Shoshone, Paiute, and Nez Perce relied on Lomatium as a remedy for respiratory ailments, including bronchitis, influenza, tuberculosis, and pneumonia. The roots were often prepared as decoctions, infusions, or poultices to ease coughs, sore throats, and congestion.

Native Americans chewed on the root to treat a range of respiratory infections. Lomatium was used for conditions including cold, flu, bronchitis, tuberculosis, hay fever, asthma, and pneumonia. It was also used in a tobacco mixture; the herb was smoked during rituals, and healers used the smoke to treat respiratory infections. Lomatium was used when the Native Americans were exposed to tuberculosis and other diseases that Europeans brought to North America.

The plant was commonly known as Toza by the Numic-speaking tribes of the Great Basin, and was commonly used for food, medicine, and ceremonial purposes (Meilleur et al., 1990). The roots of several Lomatium species were used medicinally by the Gosiute Indians, who called the plant "pia-a-na-tsu," or "great medicine."

Documentation of Lomatium use by First Nations peoples in British Columbia was also recorded. In British Columbia, the Okanagan used Lomatium dissectum as a fish poison and an insecticide for livestock.

Use During the 1918 Influenza Pandemic

Lomatium was also historically used to combat the influenza outbreak of 1917, a practice that is still relatively common among alternative medicine practitioners today. During the flu pandemic of 1917–1918, a special root was used by the Washoe Indian tribes near Carson City, Nevada. The account of its reported use during this pandemic, including the observation by a government-contracted physician, circulates widely in herbal medicine literature, though it is based on anecdotal and non-controlled historical records rather than prospective clinical data. Long respected in herbal traditions and historically associated with use during the influenza epidemic of 1917–1918, Lomatium became a herb about which Edward K. Alstat, N.D., R.Ph., published research in 1987 exploring traditional uses and emerging evidence.

Food Use

The entire lomatium plant is edible, and numerous Native American groups regarded the lomatium plant as both a food source and medicinal remedy. All species are reported to be edible.

4. Key Phytochemical Constituents

The chemistry of Lomatium dissectum root has been investigated in a series of peer-reviewed phytochemical studies. The major compound classes identified include:

Tetronic Acids

The dichloromethane fraction of L. dissectum contains water-soluble tetronic acids, flavonoids, and three coumarin glycosides, including an apiose glycoside. The tetronic acids are antimicrobial, and both the aqueous and volatile oil fractions of L. dissectum root have demonstrated widespread antibacterial activity. These tetronic acids are described in the literature as the principal antimicrobial metabolites in crude extracts. They were isolated and found to be the principal antimicrobial metabolites in the crude extracts of the whole plant. These unstable tetronic acids were partially characterized from spectroscopic data, but chemical transformations were required to secure their complete structures.

Coumarins and Coumarin Glycosides

Investigation of Lomatium dissectum resulted in the isolation of a known flavonoid and three coumarin glycosides, two of which were previously unreported. One of these new compounds contains apiose, a sugar uncommon in coumarins. The coumarins identified in various Lomatium species include furanocoumarins (nodakenetin, columbianin), pyranocoumarins (including columbianadin), and the angular pyranocoumarin suksdorfin (isolated specifically from the related species Lomatium suksdorfii). Coumarins in Lomatium are being investigated for their possible usefulness in treating HIV infection.

Flavonoids

One source suggests the constituents tetronic acids and a glucoside of luteolin may be potentially antiviral. However, little is known about how these compounds act or if other ones might be as important.

Volatile Oils

L. dissectum var. dissectum essential oils are dominated by octyl acetate and decyl acetate; by contrast, L. papilioniferum essential oils from western Idaho have high p-cymene and 2-methyl-5-(1,2,2-trimethylcyclopentyl)phenol concentrations, while those from Oregon have relatively high β-phellandrene and sedanenolide levels. The 2025 chemotaxonomic study by Setzer et al. analyzed essential oil compositions across seven Lomatium species using hydrodistillation and gas chromatographic methods, examining L. anomalum, L. dissectum var. dissectum, L. multifidum, L. nudicaule, L. packardiae, L. papilioniferum, and L. triternatum var. triternatum from Oregon and Idaho.

Resins and Other Constituents

Lomatium's antimicrobial activity is due to the tetronic acids and glucoside of luteolin that it contains. Other ingredients include the resin, which causes rash in some people, and coumarins, which could possibly cause rash as well. The ichthyotoxicity of plant extracts has been traced to the tetronic acids isolated in phytochemical investigation. Additional constituents reported include gums, oleo-resins (terpenes and sesquiterpenes), carbohydrates, protein, fatty acids, ascorbic acid, methylamines, valeric acid, saponins, and tannins.

5. Proposed Mechanisms of Action

Antimicrobial Activity

Both the aqueous and volatile oil fractions of L. dissectum root have demonstrated widespread antibacterial activity. The purported effect of L. dissectum in the treatment of respiratory tract infections may be due to a combination of direct antibacterial effects and immunomodulatory effects.

Immunomodulation via CXCL10 Inhibition

Evidence suggests that dysregulation of cytokines and chemokines, including CXCL10, is the primary factor leading to poor prognosis in highly pathogenic influenza infection. A 2014 cell-based study was conducted to address the hypothesis that an aqueous extract of L. dissectum root inhibits CXCL10 secretion by human bronchial epithelial cells stimulated with polyinosinic:polycytidylic acid (poly i:c), a synthetic analog of viral dsRNA. Results showed that L. dissectum root aqueous extract at 1 µg/mL significantly inhibited CXCL10 secretion (P=0.043, ANOVA, Tukey HSD) and demonstrated maximal inhibition 6 h post poly i:c exposure. MTT cytotoxicity assay results suggest that this inhibitory effect was not due to extract-induced cytotoxicity.

Photosensitizing Coumarins

Psoralen-containing herbs such as some angelica species and Lomatium dissectum are classified among photosensitizing agents capable of causing skin reactions. The furanocoumarins present in the plant may be responsible for both photosensitizing properties and some of the observed skin rash reactions.

Anti-HIV Pyranocoumarin Activity (Genus-level)

In a related Lomatium species, L. suksdorfii, a pyranocoumarin compound called suksdorfin was investigated for anti-HIV activity. Suksdorfin, isolated from the fruit of Lomatium suksdorfii, was found to inhibit HIV-1 replication in the T cell line H9 with an average EC50 value of 2.6 ± 2.1 µM. Suksdorfin was also suppressive during acute HIV-1 infections of peripheral blood mononuclear cells, monocyte/macrophages, and the promonocytic cell line U937. Combinations of suksdorfin and the anti-HIV nucleosides ddI and ddC demonstrated statistical synergy in inhibiting HIV-1 replication (ddC > ddI). Comparison of the structure and activity of suksdorfin with those of ten related compounds indicated that the dihydroseselin type of pyranocoumarin possessing a 4′-isovaleryl group is important to suksdorfin's enhanced anti-HIV activity. Subsequent medicinal chemistry work used suksdorfin as a scaffold for the development of the analogue 3′R,4′R-di-O-camphanoyl-(+)-cis-khellactone (DCK). Mechanism-of-action studies indicate that DCK and its analogues have a novel effect, preventing the production of double-stranded viral DNA from the single-stranded intermediate; this is different from traditional reverse transcriptase inhibitors, which block the generation of single-stranded DNA from the RNA template. All of this work is in the context of L. suksdorfii and laboratory models only; no clinical data exist for L. dissectum in HIV treatment.

6. Scientific Evidence by Area of Use

General evidence level caveat: Despite its historical use and anecdotal support, there is a lack of robust scientific evidence to substantiate therapeutic claims. No double-blind, placebo-controlled studies have been conducted to determine Lomatium's effectiveness, and the evidence suggesting its antiviral properties is weak and primarily based on preliminary test-tube studies.

6.1 Respiratory Infections and Influenza

In vitro and cell-based evidence: One hundred methanolic plant extracts were screened for antiviral activity against seven viruses. Twelve extracts were found to have antiviral activity at non-cytotoxic concentrations tested. A Lomatium dissectum root extract completely inhibited the cytopathic effects of rotavirus in this 1995 Journal of Ethnopharmacology screen (McCutcheon et al.). This is an in vitro finding with no established clinical correlate.

A 2014 cell-based study published in the Journal of Restorative Medicine (Zamechek & Wenner) examined whether aqueous root extract could inhibit CXCL10 secretion from human bronchial epithelial cells (BEAS-2B) stimulated with the viral RNA analog poly i:c. The study used BEAS-2B cells treated with poly i:c, which were exposed to L. dissectum root aqueous extract simultaneously or at 2 h intervals up to 8 h post-stimulation. The authors reported that this was the first report of an inhibitory effect of an aqueous L. dissectum root extract on CXCL10 secretion, a chemokine implicated in the pathogenesis of influenza A infection. This inhibitory effect was not due to cytotoxicity of the extract on BEAS-2B cells. L. dissectum significantly inhibited CXCL10 secretion when added up to 6 h post poly i:c stimulation, suggesting that aqueous L. dissectum root extract may be useful as treatment during influenza virus infection. The authors concluded that the observation that L. dissectum extract inhibits CXCL10 secretion provides a plausible mechanism for the efficacy reported in ethnobotanical studies and case reports, and that L. dissectum may reduce morbidity and mortality associated with influenza and merits further research. The authors noted that more in-depth investigations of immunomodulatory effects are needed, and that this preliminary investigation is limited in that the results may be due to unidentified microbially-derived elements or other impurities in the root extract.

Clinical/human evidence: No controlled clinical trials have been published examining the efficacy of Lomatium dissectum extracts in human patients with influenza or other respiratory infections. Modern scientific research on Lomatium remains limited, with several laboratory and ethnobotanical studies continuing to explore the plant's traditional applications and phytochemistry. Evidence strength for respiratory use is therefore preliminary and preclinical only.

6.2 Antibacterial Activity

An antibiotic screening study of British Columbian medicinal plants (McCutcheon et al., 1992, Journal of Ethnopharmacology) tested Lomatium dissectum root extract against a panel of bacterial strains. Fernleaf biscuitroot has been shown to possess antiviral and antibiotic properties (McCutcheon et al., 1992; 1995). The tetronic acids are antimicrobial, and both the aqueous and volatile oil fractions of L. dissectum root have demonstrated widespread antibacterial activity. Evidence is derived from in vitro laboratory screening; no clinical trials in bacterial infections have been conducted.

6.3 Antifungal Activity

In a 1994 antifungal screening study (McCutcheon et al., Journal of Ethnopharmacology), one hundred methanolic plant extracts were screened for antifungal activity against 9 fungal species. Eighty-one were found to have some antifungal activity, and 30 extracts showed activity against 4 or more of the fungi assayed. Antifungal agents from Lomatium dissectum were also reported in an abstract at the International Research Congress on Natural Products (Cardellina & VanWagenen, 1985). All evidence is in vitro; no clinical antifungal trials exist.

6.4 Anti-HIV Research (Genus-level; L. suksdorfii)

In 1994, Kuo-Hsiung Lee and colleagues isolated the pyranocoumarin suksdorfin from Lomatium suksdorfii by bioactivity-directed fractionation and anti-HIV-1 assays in H9 lymphocytes. Lee and colleagues isolated suksdorfin from Lomatium suksdorfii, which demonstrated inhibition of HIV-1 replication in H9 cells with EC50 = 1.3 µM and TI = 79. Subsequently, a number of suksdorfin 3′,4′-analogs were synthesized, among which 3′,4′-di-O-camphanoyl-cis-khellactone (DCK) inhibits HIV-1 replication in H9 cells with EC50 = 0.41 nM and TI > 78,000. This research is entirely laboratory-based, from a different species (L. suksdorfii) rather than L. dissectum, and has not progressed to human clinical trials. Evidence strength: in vitro only, not applicable to supplement use of L. dissectum.

6.5 Immunomodulatory Activity

The CXCL10 inhibition study described above (Section 6.1) represents the primary peer-reviewed evidence for immunomodulatory activity. Early and excessive production of CXCL10 is also associated with poor prognosis in other conditions such as ARDS, hepatitis, SARS-CoV infection, inflammatory bowel disease, and other autoimmune conditions. L. dissectum warrants further investigation as a novel treatment for the prevention of influenza-associated morbidity and mortality and for other diseases associated with CXCL10 dysregulation. Evidence is limited to a single cell-based study; no human immunological trials have been published.

7. Body Systems and Health Areas Associated with Lomatium

Based on the available traditional use records and laboratory evidence, Lomatium dissectum is primarily associated with the following body systems and health areas:

• Respiratory system: The predominant area of traditional use and the focus of most laboratory research. In the herbal medication literature, Lomatium dissectum is characterized as an expectorant and treatment for febrile respiratory illnesses. Conditions historically addressed include colds, influenza, bronchitis, pneumonia, and tuberculosis.
• Immune system: Traditional accounts and the CXCL10 study suggest immunomodulatory activity. The plant is classified by herbal practitioners as an immunostimulant.
• Antimicrobial / infectious disease: In vitro data support antibacterial, antiviral, and antifungal screening activity across several microbial targets.
• Skin: Historically used as a wound-healing and topical remedy. Ironically, a notable adverse event associated with its use is a whole-body maculopapular rash (discussed in the Safety section below).
• Urinary tract: Traditional uses have included an intestinal and urinary antiseptic role.

8. Dosage Forms and Reported Dosages

There are no clinically validated dosage recommendations for Lomatium dissectum based on controlled human trials. The dosages below are drawn exclusively from sources that report what has been used or recommended in herbal practice literature:

• Resin-free lomatium isolate (oral liquid): According to sources, lomatium is reputed to have antiviral effects. One source suggests the constituents tetronic acids and a glucoside of luteolin may be potentially antiviral. Lomatium extracts with the resins removed (often called lomatium isolates), 1–3 ml per day, have been recommended.
• Lomatium tincture (full extract): Lomatium tincture, 1–3 ml three times per day, can also be used, but it may cause a rash in susceptible people. The tincture should not be used unless a very small amount of it is first tested for a reaction. However, even very small amounts can cause a reaction in sensitive people.
• High-dose caution: A high dosage of the herb may result in nausea.
• Research dose: In the 2014 Zamechek & Wenner cell study, L. dissectum root aqueous extract at 1 µg/mL significantly inhibited CXCL10 secretion; this is an in vitro concentration and does not translate directly to a human dose.

9. Safety Considerations and Interactions

The Characteristic Skin Rash

The most consistently documented adverse event associated with Lomatium dissectum use is a whole-body skin rash, which has been reported in peer-reviewed case reports.

A 2018 case report published in the Kansas Journal of Medicine by Marshall and Thornton (University of Kansas Health System, Department of Emergency Medicine) described what was characterized as a report novel to the peer-reviewed medical literature of an adverse event due to the use of an herbal remedy for influenza. A 74-year-old woman with a history of hypertension and coronary artery disease presented to the ED with a diffuse, intensely pruritic maculopapular rash of four days' duration. She denied any medication changes, reporting only her longstanding use of hydrochlorothiazide, lisinopril, and clopidogrel.

A second case was published in the peer-reviewed Annals of Allergy, Asthma & Immunology. This case described an adverse reaction to Lomatium dissectum when it was used for prophylaxis against COVID-19 infection. A 57-year-old female presented with a 1-day history of a diffuse red, itchy rash. She had been in good health prior to this and her only daily medications were magnesium and vitamins. Six days prior to presentation she began taking Lomatium dissectum extract. The day prior to her visit, she developed rapid-onset, body-wide rash that was intensely pruritic. Physical examination revealed an afebrile patient in moderate distress from a diffuse maculopapular rash, sparing only the palms and soles. A rash that occurs in the first week of treatment, lasting for 5 days, is described as a possible side effect. Allergists should be aware of this possible adverse drug reaction when evaluating patients for acute rash reactions.

Reportedly, lomatium resin frequently causes allergic reactions, leading to a whole-body rash; this is why resin-free products are sold. Other ingredients include the resin, which causes rash in some people, and coumarins, which could possibly cause rash as well.

Photosensitization

Psoralen-containing herbs such as some angelica species and Lomatium dissectum are listed among photosensitizing agents that can cause skin rashes. The furanocoumarins present in the plant are structurally related to psoralens, which are established photosensitizers.

Potential Drug Interactions

Lomatium dissectum contains coumarin derivatives and may increase the risk of bleeding. It should not be taken with anticoagulants (blood thinners) and immunostimulants, as Lomatium root has been reported to intensify the effects of these two groups of drugs.

Pregnancy

Because there is limited information about effects on a fetus, lomatium should not be taken while pregnant.

Nausea at High Doses

High doses of Lomatium dissectum may cause nausea.

Absence of Formal Safety Testing

Lomatium has not undergone any modern formal safety testing. Furthermore, the safety of Lomatium has not been thoroughly assessed, with reports of allergic reactions and digestive discomfort associated with its use. While Lomatium is recognized for its traditional uses, further research is needed to validate its therapeutic efficacy and ensure safety for various populations.

10. Summary of Evidence Strength

Despite promising laboratory evidence and a long history of use in traditional medicine, clinical validation of Lomatium dissectum's efficacy in humans remains limited. Few, if any, well-controlled studies have been conducted to substantiate its health benefits or safety profile. While Lomatium dissectum continues to be included in various nutritional supplements and herbal products, further research is needed to fully understand its therapeutic potential and mechanisms of action.

The current state of evidence can be summarized as follows:

• Antiviral (rotavirus, influenza — in vitro): Positive signals from cell and culture studies; no human trials.
• Immunomodulatory / CXCL10 inhibition: A single in vitro cell study; preliminary and requiring replication.
• Antibacterial / antifungal: Multiple in vitro screening studies; no clinical trials.
• Anti-HIV (suksdorfin from L. suksdorfii): In vitro laboratory data only; no clinical translation.
• Respiratory illness / influenza (human): Traditional ethnobotanical use and case reports only; no randomized controlled trials.

References

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• Lomatium Dissectum Rash: A Complication of COVID-19 Prophylaxis Therapy. Annals of Allergy, Asthma & Immunology, 2020 — PMC
• Zamechek D, Wenner CA. "Lomatium dissectum Inhibits Secretion of CXCL10, a Chemokine Associated with Poor Prognosis in Highly Pathogenic Influenza A Infection." Journal of Restorative Medicine, 2014
• McCutcheon AR, Roberts TE, Gibbons E, et al. "Antiviral screening of British Columbian medicinal plants." J Ethnopharmacol. 1995;49(2):101-110 — PubMed
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• Lee TT, Kashiwada Y, Huang L, et al. "Suksdorfin: an anti-HIV principle from Lomatium suksdorfii, its structure-activity correlation with related coumarins, and synergistic effects with anti-AIDS nucleosides." Bioorg Med Chem. 1994;2(10):1051-1056 — PubMed
• Setzer WN, Poudel A, Satyal P, et al. "Lomatium Species of the Intermountain Western United States: A Chemotaxonomic Investigation Based on Essential Oil Compositions." Plants. 2025;14(2):186 — PMC
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