Cat's claw is an herb popular among the indigenous people of Peru, where it is used to treat cancer, diabetes, ulcers, arthritis, and infections, as well as to assist in recovery from childbirth. It is also used as a contraceptive. There are two primary species of cat’s claw used medicinally: Uncaria tomentosa and Uncaria guianensis.

Cat's claw is most often marketed as a treatment for viral diseases, such as herpes, shingles, AIDS, and feline leukemia virus. However, the evidence for these uses is extremely preliminary.

The most meaningful study yet performed on cat's claw suggests that the Uncaria guianensis species might be helpful for an entirely different condition: osteoarthritis.3

In addition, one double-blind trial indicates that a certain type of Uncaria tomentosa may be modestly helpful for people with rheumatoid arthritis.5

Cat's claw has also been proposed as a treatment for allergies and stomach ulcers, but there is no meaningful evidence as yet that it is effective for these conditions.