Answer
Jul 28, 2026 - 01:55 PM
If cantharidin stays on longer than instructed, it can keep damaging the outer skin and cause:
- Excessive or unusually large blisters
- Severe burning and pain
- Raw or eroded skin similar to a chemical burn
- Prolonged healing, discoloration and, rarely, scarring
- A higher risk of infection if the skin opens
Wash it off now with mild soap and water if the instructed time has passed or you have severe pain or blistering. Do not scrub or use a rough washcloth. The correct wash-off time depends on the product: FDA-approved YCANTH is normally removed after 24 hours, while some compounded cantharidin treatments may be removed after only 4–8 hours—follow your clinician’s instructions.
Contact the treating clinician promptly for severe or increasing pain, extensive blistering, spreading redness, pus, fever, or difficulty walking. If it entered the eye, rinse continuously with water for at least 15 minutes and seek urgent medical care.
