Cantharidin for Molluscum Contagiosum
Molluscum contagiosum is a virus that commonly causes warts in children. As the name suggests, it is contagious, with an incubation period of up to 90 days. This means that if you have developed warts due to molluscum, it is likely that you came into contact with someone with the virus up to 3 months prior to developing the lesions. Cantharidin is one of many treatments for molluscum contagiosum.
Cantharidin, the active ingredient in Cantharone, is a potent blistering agent derived from the dried, powdered blister beetle. This “blister beetle juice” is commonly used to treat molluscum because it is painless upon application and kills warts by forming a blister under the wart separating it from its blood supply. It is applied in the office to specific lesions and allowed to dry. It must be washed off with soap and water 4 hours after application, or sooner if any pain, burning or discomfort occurs.
Treatment Progression (as a general rule, patients can expect the following)
At time of application no pain or discomfort should be experienced.
4 hours: Mild discomfort may occur; wash affected areas with soap and water.
24 hours (or sooner): Blistering usually forms by 24 hours, separating the wart from its blood supply. The blister is usually filled with clear yellow fluid, but it is not uncommon to have blood in the blister fluid.
4 days: Crusted blister falls off leaving superficial erosions. Treat with Vaseline twice daily
7 days: Lesions are usually healed with temporary residual inflammation or redness. Temporary loss of normal pigmentation often occurs, but usually no scarring.
Although most patients note little discomfort, some may experience tingling, itching, or burning. The area may be tender for several days. Acetaminophen or ibuprofen may be given for discomfort. Soaking the area with cool water compresses may also provide relief. If present, a blister may be punctured with a sterile needle if it is uncomfortable. Otherwise, leave the blistered skin intact to provide a natural band-aid. You can apply over-the-counter topical antibiotic ointment, such as Aquaphor, Vaseline, or a generic substitute.
It is not uncommon to need repeated treatments and although highly effective, Cantharone will not work for all warts. Appointments should be scheduled at 4 week intervals for optimal results.