Cantharidin cream for molluscum is a topical treatment commonly used to manage this skin condition, but does it really work?
Cantharidin is a topical blistering agent (vesicant) that is commonly used for the treatment of molluscum. The mechanism of action is that it is a keratolytic agent (dissolves keratin on the skin) and thought to cause molluscum exfoliation via its acantholytic (cell dissolving) actions.
Typically, cantharidin is applied to clean skin using an applicator stick and usually covered for a few hours. Within 24 hours, a blister forms, and healing is typically evident within 7 days.
Treatments are usually repeated every two to four weeks until all lesions have resolved. In general, treatment with cantharidin should be avoided on the face or groin areas.
Treatment should be performed by a clinician only and patients are not given cantharidin to be applied at home. The expected response is the development of a small blister at the treatment site, followed by disappearance of the molluscum lesion and healing with or without scarring.
Although cantharidin is a common treatment, the effectiveness of cantharidin cream for molluscum is uncertain at best. A recent clinical trial in which 94 children with molluscum contagiosum were randomly assigned to a single treatment of cantharidin without occlusion, cantharidin with occlusion, placebo without occlusion, or placebo with occlusion found a non-statistically significant trend towards better outcomes with cantharidin. Total clearance of molluscum lesions at week 6 occurred in 10 of 24 children (42 percent) in the cantharidin with occlusion group, 7 of 23 children (30 percent) in the cantharidin without occlusion group, 2 of 25 children (8 percent) in the placebo with occlusion group, and 3 of 22 children (14 percent) in the placebo without occlusion group. A post-hoc analysis that compared the combined cantharidin groups with the combined placebo groups found the response to cantharidin superior (36 versus 11 percent of patients achieved complete clearance, respectively).
In another recent retrospective study of 300 children treated with cantharidin (without occlusion) for molluscum, 90 percent of children had lesion clearance, and an additional 8 percent demonstrated improvement without complete clearance. On average, about two clinician visits were necessary to achieve complete clearance. The parents of the patients appeared satisfied with treatment; 95 percent stated that they would be willing to have their child treated again with cantharidin.
Common adverse effects of cantharidin include temporary burning, pain, erythema, and itching. Postinflammatory dyspigmentation (darkening) of the skin may occur, but typically resolves over several months. While somewhat uncommon, scarring can occur as a consequence of cantharidin treatment.
In conclusion, while cantharidin cream for molluscum is widely used, its effectiveness varies, and further research may be necessary to fully understand its efficacy.