Avoid in individuals with a known allergy or hypersensitivity to desert parsley (Lomatium dissectum).

Desert parsley is generally recognized as safe in traditional and historical sources. However, resins in desert parsley extracts may cause rash in susceptible people that may not be improved with cortisone or antihistamine. To avoid this rash, traditional sources suggest using lomatium isolates, with the resins removed. Unsubstantiated sources also recommend testing a small area with the tincture for a reaction before using, to reduce the possibility of a reaction.

High doses of desert parsley may result in nausea. Desert parsley contains coumarin derivatives and may increase the risk of bleeding.

Desert parsley is not recommended in pregnant or breastfeeding women due to a lack of available scientific research.

There is no proven safe or effective dose for desert parsley. Nonetheless, desert parsley extracts with the resin removed (lomatium isolates) have been taken in doses of 1-3 milliliters daily. Desert parsley has also been taken by mouth as a tea or tincture.

There is no proven safe or effective dose for desert parsley in children.

Lomatium dissectum contains coumarin derivatives. Thus, desert parlsey may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Although not well studied in humans, the methylene chloride extract of Lomatium californicum seeds showed antifungal activity against Colletotrichum fragariae. Caution is advised when taking desert parsley with other antifungal agents due to additive effects.

Although not well studied in humans, Lomatium species may inhibit HIV-1 replication. Caution is advised when taking with antiviral agents due to additive effects.

Lomatium dissectum contains coumarin derivatives. Thus, desert parsley may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

Although not well studied in humans, the methylene chloride extract of Lomatium californicum seeds showed antifungal activity against Colletotrichum fragariae. Caution is advised when taking desert parsley with other herbs with antifungal activity due to additive effects.

Although not well studied in humans, Lomatium species may inhibit HIV-1 replication. Caution is advised when taking with antiviral agents due to additive effects.