Cantharidin

Description: Cantharidin, which is produced by certain species of beetle, has been used for centuries to treat ulcers, tuberculosis, and other conditions. It is now used mostly as a potent vesicant to treat benign skin growths including molluscum contagiosum and warts. Catharidin had FDA approval as a blistering agent until 1962, when the criteria for approval were changed. In 1997 the FDA Modernization Act made room for cantharidin-containing products to be made by compounding pharmacies.

How Cantharidin Works

When applied correctly in the right dosage, cantharidin is safe and effective with fewer adverse effects than other treatments. Multiple reports have concluded that cantharidin should be a first-line treatment for molluscum contagiosum and warts. In one study that included 300 pediatric patients with molluscum contagiosum, 90% experienced clearance and no major side effects were reported.

Cantharidin works by blistering tissues, which causes tissues that contain certain viruses to separate from the surrounding skin. The process through which this happens is called acantholysis. It is an effective way to treat molluscum contagiosum because the skin heals afterwards without scarring. Blisters will form about 24 to 48 hours after application and heal within 4 to 7 days. The benefits of cantharidin compared to other destructive treatments are that application is painless and there is no permanent scarring. There may be hyperpigmentation or hypopigmentation that lasts longer after the skin has healed but this usually will clear over a few months.

Applying Cantharidin

Because of its high potency and risk of toxicity if applied incorrectly, application should only be done by a healthcare professional in-office and not by a patient at home. With a cotton swab, apply one layer of cantharidin to the affected area. It should only be applied to a few small areas at a time to minimize any systemic absorption. For a pediatric patient with molluscum contagiosum, no more than four or five lesions should be treated in the first visit and no more than 12 to 15 in subsequent visits.

External Links

• Childhood molluscum contagiosum: Experience with cantharidin therapy in 300 patients – Journal of the American Academy of Dermatology
• Use of Cantharidin for Verruca – Podiatry Institute
• Cantharidin Revisited: A Blistering Defense of an Ancient Medicine – JAMA Network