Cantharidin
What is cantharidin?
Cantharidin is a blistering medication that has long been used in dermatology for selected skin lesions, especially molluscum contagiosum and certain warts. It is typically applied in the office rather than used as a home medication. A newer branded cantharidin product, Ycanth, is specifically used for molluscum contagiosum in appropriate patients.
It is best understood as a procedural medication used by clinicians rather than a cream or pill that patients use on their own.
How does cantharidin work?
Cantharidin works by causing a controlled blistering reaction in the outer layers of the skin. This can help destroy or lift the treated lesion over time. Because the reaction can be strong if too much is used or if it stays on too long, treatment instructions matter.
That controlled reaction is also the reason careful timing and wash-off instructions are so important after treatment.
What are possible side effects of cantharidin?
Expected effects can include blistering, redness, burning, tenderness, crusting, and temporary discomfort in the treated area. Some patients may also develop temporary darkening or lightening of the skin after treatment. Because the goal is often to create a controlled reaction, some irritation is expected, but severe or excessive reactions should be discussed with your provider.
In children especially, families should be told in advance that the treated spots may look worse for a short period before they improve.
How is cantharidin used?
Cantharidin is usually applied by a healthcare professional directly to selected lesions and then washed off later as directed. The exact timing depends on the product used, the body location, and the treatment plan. Ycanth is a cantharidin-based option used for molluscum contagiosum and is also applied in the office rather than self-applied at home.
Patients are usually given clear after-care instructions about washing the medicine off, protecting the area, and what to do if blistering becomes more intense than expected.