Cantharidin is a potent blistering agent/vesicant naturally derived from the blister beetle, most famously the “Spanish fly” (Lytta vesicatoria).
Tradename Ycanth.
It is used as a topical treatment for viral skin infections, specifically molluscum contagiosum and warts.
Cantharidin is applied exclusively by healthcare professionals in a clinical setting to ensure precision and safety.
Cantharidin) is the first prescription treatment for this viral infection in adults and children aged 2 and older.
Warts: It is used to treat common, plantar, and periungual warts by inducing a controlled blister.
It is absorbed by the lipids in the cell membranes of the epidermis.
It triggers the release of serine protease enzymes that break down the proteins holding skin cells together, leading to acantholysis or,detachment of skin cells,and the formation of a blister.
The blister eventually lifts the viral growth off the skin so it can slough away.
Patients typically experience blistering, redness, itching, scabbing, and localized pain at the application site.
Temporary lightening or darkening of the skin (post-inflammatory pigment alteration) may occur, though permanent scarring is rare when used correctly.
Severe Risks: Contact with the eyes can cause severe injury, ulcers, and permanent vision loss.
It is also highly flammable even after drying on the skin.
Systemic Toxicity: If swallowed, cantharidin is extremely poisonous and potentially fatal. Ingestion can lead to renal failure, gastrointestinal damage, seizures, and respiratory paralysis.
The liquid is applied to the lesion; it may be covered with nonporous tape for 4–6 hours.
The area must be washed with soap and water after the prescribed duration, usually 4–24 hours depending on the product.
A blister typically forms within 24–48 hours and heals within 4–7 days.
Multiple treatments (typically 3–6) may be necessary for full resolution of the lesions.
Ycanth (cantharidin) 0.7% Topical Solution: The first and currently only FDA-approved cantharidin product for molluscum contagiosum.
Canthacur (0.7% cantharidin): A liquid preparation often used for common warts and molluscum.
Canthacur PS (1% cantharidin / 30% salicylic acid / 2% podophylotoxin): A more potent formulation specifically indicated for resistant plantar warts.