I used Retin A on a large freckle it cause it to peel and scab over. The scab kept coming off when I took a shower. I I have been to a dermatologist and a cosmetic surgeon. The first opinion which was the cosmetic surgeon said it was nothing.....the dermatologist wants to do a biopsy. He thinks it might be the beginnings of a melanoma, but very early early stage. I also have a strange purple mark on my face near a scar from a face lift. He thinks perhaps we should biopsy that too.