Physical Modalities: Cantharadin  

Cantharidin is a topical substance derived from the blister beetle, and when applied acts as a vesicant and causes localized blistering of the skin. It is frequently used to treat molluscum, and occasionally for small, thin warts. This is a physician-applied treatment. A small drop is applied to the lesion using the wooden end of a cotton swab and allowed to dry completely.  This is a painless procedure and is tolerated even by young children.  The lesion should be washed with soap and water after 2-4 hours.  Some patients develop large blisters and so only a few lesions should be treated initially.  Retreatment can occur after 2-4 weeks.  Warts can also be treated with cantharidin; however, ring warts can develop after such therapy.