I am very fair skinned with freckles and of Irish ancestry. At age 50, I have just been prescribed fluorouracil for precancerous/dry skin on my face and hands. A couple of years ago, I had a few small spots on my back frozen off, as I also had today. My doctor said I could do the treatment for two weeks, let it heal, and then repeat treatment and healing process. She said doing it gradually might be better for me and that most people who split the process find that the second time round isn't as bad as the first. Or I could wait until the end of the summer and do it all at once if it doen't become too irritated.