Dear Deborah,   Efudex, a prescription cream containing 5-fluorouracil, is applied to the skin to treat actinic keratoses - red scaly precancerous skin growths.  During treatment, your skin usually becomes red and flaky and may develop crusting or oozing. The more actinic keratoses you have, the more intense this skin reaction may be. If the reaction is so intense that it's uncomfortable, your dermatologist may advise you to decrease the number of times per week that you are applying the Efudex or even to take a hiatus from using it. It's very important to be aware that Efudex makes you more sensitive to the sun, so you are more prone to sunburn in the skin areas to which you're applying it. It's best to wear a broad spectrum (UVA and UVB protectant) sunscreen with SPF of 30 or above while using Efudex. Another option for treating actinic keratoses at home is prescription Aldara cream, which contains the active ingredient, imiquimod. Aldara works by specifically stimulating your skin's immune system to destroy the actinic keratoses. Aldara has been shown in a number of studies to be more effective than Efudex, it tends to cause less skin irritation and does not cause sun sensitivity. Aldara is also FDA approved for treatment of some types of skin cancer. The only problem is that it may not be covered by all health insurance plans.   Best regards, Dr. Hema