Lomatium is a wild plant native to the western United States, used primarily as an herbal remedy for respiratory infections, including colds, flu, and bronchitis. Its root has been a staple of Native American medicine for centuries, and it gained wider attention after reports that indigenous communities using lomatium during the 1918 influenza pandemic experienced unusually low rates of infection. Today it is sold as tinctures, capsules, and dried root preparations, though it lacks approval as a pharmaceutical treatment and has limited clinical research in humans.
Traditional and Historical Uses
Native American peoples in the western U.S. relied on lomatium root (specifically the species Lomatium dissectum, sometimes called “desert parsley” or “biscuitroot”) to treat respiratory illness long before European contact. The root was typically prepared as a decoction or chewed directly. Its uses extended beyond the lungs to include general infections and fever.
The plant’s most famous historical moment came during the 1918 Spanish flu pandemic. Ethnobotanical accounts note that Native American populations who used lomatium had low rates of influenza infection compared to surrounding communities. These observations were anecdotal rather than controlled, but they cemented lomatium’s reputation among herbalists and drove its popularity in natural medicine circles throughout the 20th century.
How Lomatium Works in the Body
Researchers have identified several groups of active compounds in lomatium root. The principal antimicrobial substances are a pair of compounds called tetronic acids, which were isolated from the whole plant and confirmed as the main drivers of lomatium’s germ-fighting activity in laboratory settings. The plant also contains other bioactive compounds, including ones that show antibacterial effects against common bacteria like Staphylococcus aureus (the bacterium behind staph infections) and Bacillus subtilis.
On the antiviral side, lab studies have shown activity against viruses such as rotavirus (a common cause of stomach illness). More recently, researchers found that lomatium extract inhibits the release of a specific inflammatory signaling molecule that is associated with poor outcomes in severe influenza infections. In simpler terms, the plant may help by calming an overactive immune response during the flu, not just by attacking the virus directly. This finding, published in the Journal of Restorative Medicine, offers a plausible biological explanation for the historical reports of lomatium’s effectiveness against influenza.
Common Modern Uses
Herbalists today recommend lomatium primarily for:
- Colds and flu: Taken at the first sign of symptoms, usually as a tincture, to reduce severity and duration of upper respiratory infections.
- Bronchitis and chest congestion: Used to help clear mucus and support recovery from lower respiratory infections.
- General immune support: Some people take low doses during cold and flu season as a preventive measure.
It is important to note that these uses are based on traditional practice and limited laboratory research, not on large-scale human clinical trials. No standardized dosing guidelines exist, and the potency of commercial products varies widely depending on the manufacturer, the plant part used, and the extraction method.
Available Forms
Lomatium root is most commonly sold as a liquid tincture (an alcohol-based extract), which is the form most herbalists prefer because it preserves the plant’s volatile compounds. You can also find it in capsule form, as a dried root for making tea, and in combination formulas blended with other immune-supporting herbs like echinacea or elderberry. Some products are labeled “lomatium isolate” or “LDI,” which refers to a processed extract with certain compounds removed to reduce the risk of side effects.
The Lomatium Rash
The most well-known side effect of lomatium is a full-body rash that can appear in some people who take the whole root extract. This reaction is distinctive enough that it has its own name in herbal medicine circles: the “lomatium rash.” It typically presents as a widespread, measles-like skin eruption that can last for days to weeks. The rash is not considered dangerous, but it can be uncomfortable and alarming.
The exact percentage of people affected is not well established, and the reaction appears to be idiosyncratic, meaning it is hard to predict who will develop it. Products labeled as “lomatium isolate” have had the resinous compounds thought to trigger the rash removed, and many herbalists recommend these preparations for first-time users or people with sensitive skin. Starting with a very small dose and increasing gradually is a common strategy to test tolerance.
Safety Considerations
Beyond the rash, lomatium’s safety profile is not thoroughly studied. The plant contains furanocoumarins, a class of compounds found in many plants in the carrot family that can increase skin sensitivity to sunlight. If you are taking lomatium, prolonged sun exposure may raise your risk of sunburn.
The safety of lomatium during pregnancy and breastfeeding is unknown, and health systems like PeaceHealth advise against its use in these populations. People taking prescription medications, particularly blood thinners or immune-suppressing drugs, should be cautious, as lomatium’s effects on drug metabolism have not been studied. There is also no reliable safety data for use in children.
What the Evidence Actually Shows
Lomatium sits in a common spot for traditional herbs: promising historical use and interesting lab findings, but a near-complete absence of human clinical trials. The lab data confirms real antimicrobial and antiviral activity. The historical pandemic accounts are compelling but uncontrolled. The mechanism involving inflammatory signaling is biologically plausible. None of this adds up to the kind of evidence that would support a medical claim of efficacy.
For people who choose to use lomatium as part of their approach to respiratory infections, the practical reality is that you are relying on a long tradition of use and early-stage science rather than proven clinical outcomes. Choosing a reputable manufacturer, starting with small doses, and watching for the characteristic rash are the most common pieces of guidance from experienced herbalists.