Although no serious adverse effects have been reported for cat’s claw, there is little known about its safety because most reports have been based on anecdotal evidence. There is one case report in which Parkinson's disease became worse after a man started using cat's claw and improved after cat's claw was discontinued.¹³ Cat’s claw should be used with caution in people with autoimmune illness, multiple sclerosis, and tuberculosis. Until proven safe, cat’s claw should not be taken by pregnant or breast-feeding women.