MODEL RELEASED. Chemical burn on forehead from drug treatment. The 65-year-old man had applied fluorouracil (5-FU) to his forehead to treat solar keratosis growths. This condition is also known as actinic keratosis. Solar keratoses are mostly found on areas of skin that are exposed to the sun, including the backs of hands and the face. It is important to remove the lesions as they can develop into skin cancer. They may be removed by scraping, freezing with liquid nitrogen, or surgery.