Molluscum contagiosum is a common skin infection. A topical solution, formally known as cantharidin and sometimes called “beetle juice,” is used to treat the lesions. This article explains how cantharidin works and what to expect during treatment.
Understanding Molluscum Contagiosum
Molluscum contagiosum is a common skin infection caused by a poxvirus. It primarily affects children but can also affect adults, spreading easily through direct contact or contaminated objects. The infection appears as small, raised, pearl-like bumps with a central dimple. These lesions are usually painless but can be itchy or sore. While molluscum often resolves naturally within six to eighteen months, treatment can clear widespread or bothersome lesions more quickly.
Cantharidin: The Active Ingredient
Cantharidin, commonly known as “beetle juice,” is a compound naturally secreted by blister beetles, such as the Spanish fly. It is known for its vesicant properties, meaning it causes blistering upon skin contact. Historically, cantharidin was used in traditional medicines. In modern medicine, cantharidin is formulated as a topical solution for professional application to skin lesions. The U.S. Food and Drug Administration (FDA) approved a topical formulation of cantharidin (Ycanth) for molluscum contagiosum treatment in 2023.
Mechanism of Action
When applied to the skin, cantharidin initiates localized blistering. The compound is absorbed by epidermal cells, triggering enzymes that break down proteins crucial for cell adhesion. This disintegration causes a loss of cellular connections, called acantholysis, leading to epidermal cells detaching from underlying layers. A fluid-filled blister forms directly beneath the molluscum lesion, separating infected tissue from healthy skin and facilitating its eventual removal. Cantharidin’s action typically remains confined to epidermal cells, allowing the basal layer to remain intact and often resulting in healing without scarring.
Treatment Application and What to Expect
Application Process
Cantharidin treatment is administered by a healthcare professional in a clinical setting. The solution is carefully painted onto each molluscum lesion, often using a specialized applicator to ensure precise delivery and minimize contact with surrounding healthy skin. After application, the treated areas are typically left uncovered, as bandages are generally not recommended. Patients are usually instructed to wash off the cantharidin with soap and water after four to six hours, though it can be washed off sooner if significant discomfort occurs.
Expected Reactions
Blistering is an expected part of the treatment process and usually develops within 24 to 48 hours following application. These blisters may be mild to moderate, and some patients might experience a stinging, burning sensation, or itching. Over-the-counter pain relievers or cool compresses can help manage any discomfort.
Healing and Follow-up
The blisters will typically crust over and begin to dry within four to five days, with the treated lesions usually falling off as the skin heals. Complete healing generally occurs within four to ten days. Multiple treatment sessions, usually spaced every three to four weeks, may be necessary to achieve full clearance of the molluscum lesions. Temporary changes in skin color, such as lightening or darkening, can sometimes occur at the treated sites, which typically resolve over time.