Lomatium (Lomatium dissectum), also known as "desert parsley," has a long history of traditional use among Native American tribes and herbalists in the western United States, especially for respiratory infections such as colds and influenza. These uses were primarily based on anecdotal evidence and ethnobotanical reports, where Lomatium root was prepared as teas, tinctures, or poultices to address symptoms of coughs and viral illnesses.

The rationale for its use is rooted in observations that Lomatium appeared to support the body during viral outbreaks, particularly during the 1918 influenza pandemic, according to some herbalist accounts. Laboratory studies have identified coumarins and other phytochemicals in Lomatium with potential antimicrobial and antiviral effects in vitro. However, there are no robust human clinical trials or large-scale scientific studies that confirm its efficacy against the common cold or other viral respiratory infections. Most of the modern support is extrapolated from limited laboratory research and extensive historical use.

In summary, while Lomatium is traditionally used for colds and has some preliminary laboratory evidence suggesting antiviral activity, there is insufficient scientific validation to strongly support its efficacy. Its use remains primarily rooted in traditional herbal medicine rather than evidence-based clinical practice.