Cantharidin, often called “beetle juice” for warts, is a topical medication used by healthcare professionals to treat specific skin growths. It offers an alternative for addressing warts and similar conditions by removing affected skin.
What Cantharidin Is
Cantharidin is a chemical compound derived from blister beetles, primarily Lytta vesicatoria, also known as the Spanish fly. Historically, this substance has been used in medicine for thousands of years, with early uses documented in ancient China and by Hippocrates. In modern dermatology, Cantharidin is a purified medical substance classified as a vesicant, meaning it causes blistering when applied to the skin.
How Cantharidin Treats Warts
Cantharidin is absorbed into the outer layer of skin cells that make up the wart. Once absorbed, it triggers acantholysis, which involves the breakdown of connections between these cells. This cellular separation forms a blister directly beneath the wart, lifting it away from the healthy skin below. The treatment does not directly eliminate the human papillomavirus (HPV) but creates an environment where the wart tissue can be shed.
Cantharidin is used for common warts, plantar warts, and molluscum contagiosum. A key advantage is its non-destructive nature to deeper skin layers. The blistering primarily affects epidermal cells, leaving the basal layer intact. This generally results in healing without scarring when applied correctly, making it suitable for children or warts in visible areas.
Applying Cantharidin
Cantharidin treatment requires application by a healthcare professional in a clinical setting. The solution is painted onto the wart, and the treated area may be covered. It is generally recommended to wash off the solution with soap and water within 4 to 6 hours, or sooner if discomfort occurs. Some protocols suggest washing it off after 24 hours.
Blistering typically occurs within 24 to 48 hours as Cantharidin separates the wart from the skin. The blister may be painful for a few days. After the blister forms, it will dry and crust over, and the wart will usually fall off within several days to a week. Multiple treatments, typically every 3 weeks, may be necessary for complete resolution, sometimes requiring up to four applications.
Potential Side Effects
Cantharidin can cause side effects related to its blistering action. Common reactions at the application site include blistering, pain, redness, swelling, and itching. Pain often begins several hours after application and can last for a few days. Mild dryness, discoloration, and scabbing are also reported.
Side effects can be managed with pain medication, cool compresses, or petroleum jelly. Less common side effects include skin ulcers or changes in skin color. Avoid applying Cantharidin to open wounds, sensitive areas like the face or genitals, or to individuals with certain skin conditions. Contact a healthcare provider for signs of infection, severe pain, excessive swelling, or allergic reactions.