Cantharidin is a vesicant extracted from crushed Chinese blister beetles. Applied topically, it is absorbed into epidermal cell membranes, leading to acantholysis, intraepidermal blistering, and resolution of the lesion. Redness and transient burning sensations are among possible complications, though these effects are exceedingly rare. Use of the agent generally does not lead to scarring. However, severe blistering can occur with improper use; and ingestion, especially by children, can be fatal (Arch. Dermatol. 2001;137:1357-60).
"The raw material is very caustic and requires extreme safety precautions when handling, but once compounded with collodion, it becomes a very effective agent for use in dermatology," Ms. Grafelman of Delasco Dermatologic Lab and Supply noted.
Cantharidin is also being researched for a variety of other uses. Clinicaltrials.gov lists recently completed randomized, placebo-controlled trials for treating molluscum contagiosum in children with cantharidin and for treating cutaneous verucca vulgaris with cantharidin along with liquid nitrogen in adults.
Cantharidin has also recently been studied for its effects on cancer cells and parasites (Int. J. Oncol. 2010;37:1243-50; Exp. Parasitol. 2010;126:126-9 ).
Dr. Mancini and Dr. Sidbury said they have no financial interests in cantharidin.