Avoid in individuals with a known allergy or hypersensitivity to guayule (Parthenium argentatum), its constituents, or members of the Asteraceae/Compositae family, such as dandelion, goldenrod, ragweed, sunflower, and daisies.

Guayule is being pursued as a hypoallergenic source of latex because in laboratory studies, its proteins do not cross-react with antibodies raised against latex proteins in conventional Hevea brasiliensis latex products.

There is insufficient evidence in humans to support the use of guayule for any indication. Use guayule cautiously in patients with compromised hepatic (liver) function or taking agents metabolized by the cytochrome P450 pathways.

Guayule is not recommended in pregnant or breastfeeding women due to a lack of available scientific evidence.

There is no proven safe or effective dose for guayule in adults.

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

Guayule may interfere with the way the body processes certain drugs using the liver's cytochrome P450 system. As a result, the levels of these drugs may be altered, and may increase/decrease the effects or increase potentially serious adverse reactions. If using any medications, check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

Constituents from guayule showed cytotoxic effects on cancer cell lines. Although the clinical significance is unknown, caution is advised in patients taking anticancer agents due to unknown combined effects.

Guayule may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 system. As a result, the levels of other herbs or supplements may be too high in the blood. It may also alter the effects that other herbs or supplements possibly have on the P450 system, such as chamomile, Echinacea, oregano, and St. John's wort.

Constituents from guayule showed cytotoxic effects on cancer cell lines. Although the clinical significance is unknown, caution is advised in patients taking anticancer agents due to unknown combined effects.