Photoaging Various combination therapies, including chemical peels, 5 - fluorouracil (5-FU), topical alpha-hydroxy acids, imiquimod, photodynamic therapy, and tretinoin, have been used to reduce precancerous changes and improve the cosmetic appearance of chronically sun-damaged skin. These therapies are often effective in ameliorating superficial skin changes (eg, fine wrinkles, irregular pigmentation, sallowness, roughness, minor laxity) but have a much less pronounced effect on deeper changes (eg, telangiectasias).