As you may know, I've been devouring old paperbacks on Edgar Cayce lately as my fun time reading.
In the book I just finished, "Edgar Cayce - Sleeping Prophet," he talks about a cure for pre-skin cancer spots that worked wonders for the author (Jess Stearns).
The idea is to rub castor oil on the spots once or twice a day. (Many of Cayce's remedies involve castor oil.) He also suggests camphorated oil, but that is now illegal in the U.S., due to accidental poisonings from people ingesting even small amounts of this strong stuff.
My wife is going to try this on her spots. The technical name is actinic keratosis. I'll let you know how it works.