Botanical Name: Grindelia
Named after the gummy resin this plant produces. One distinguishing feature of this genus (i.e., Grindelia) is that the young flowers produce large amounts of this resin. Most plants used in manufacturing herbal supplements containing gumweed are native to western North America.
- Treatment of Poison Oak Skin Rash 
No Clinical Research:All other conditions.
- Gastrointestinal Upset
- Avoid or contact a licensed healthcare practitioner, if you have allergies to plants in the family Asteraceae (ragweed, chamomile, etc.), and use caution, since there is not enough research on the use of supplements containing gumweed.
- Large doses of gumweed are said to be poisonous.
There is not enough research on the use of supplements containing gumweed during pregnancy and breast-feeding, so consult a licensed healthcare practitioner before use or avoid use. 
Gumweed is not a "drug", so the best doses have not been thoroughly established. Make sure to follow the specific product instructions and take as directed on the label, or consult a licensed healthcare practitioner before use.
1. Canavan D, Yarnell E. Successful treatment of poison oak dermatitis treated with Grindelia spp. (Gumweed). J Altern Complement Med. 2005 Aug;11(4):709-10. 2. Gruenwald J, Brendler T, Jaenicke C, editors. PDR for herbal medicines. 4th ed. Montvale, NJ, USA: Thomson Healthcare; 2007.
The "-" means there is no information.