Cantherone Plus (or any brand of Cantharidin) is applied to the wart,
you let it dry until it turns white (about 2 minutes), and then is
covered with a bandaid to ensure that it is not smeared on other
areas of the skin. The medication is left on overnight (about 8 hours),
and the area is kept dry. After about 8 hours, the medication will
have penetrated sufficiently to hopefully destroy the entire wart, and
then the bandaid is removed and the area is washed to remove any
of the remaining Cantherone on the surface of the skin that will come
off. The blisters can be punctured if they are very tight and painful.
Make sure you warn the patient that the blisters will often have pus
(white blood cells) and/or blood, and there can be a substantial
amount of associated erythema. If there are fissures in the skin when
this is applied, the Cantharidin can induce a chemical lymphangitis
that will appear within the first 24 hours, and should not be confused
with a streptococcal or staphylococcal lymphangitis. Infectious
lymphangitis usually starts two or three days or later after the wart is
treated.
