After laser treatment, it is generally necessary to pay attention to sun protection to avoid hyperpigmentation. The general measures include wearing a sun hat, long-sleeved clothing and pants, or using a sunshade or an umbrella to protect against ultraviolet rays; and using sunscreen properly. In addition, do not touch or eat, do not take photosensitive substances, food or drugs containing photosensitive substances. Common photosensitive substances: (1) chemicals: there are asphalt, anthralin, amidine, halogenated water acyl aniline, bleach, sunflower musk and methyl coumarin; (2) drugs: drugs containing photosensitive substances include chlorpromazine, iproniazid, chlorothiazide, nalidixic acid, ashwagandha, sulfanilamide, tetracycline, aspirin, sodium salicylate and other antipyretic painkillers; estrogen, dihydrocoumarin, Chinese herbal medicines such as thorax, bupleurum, dock (3) food: plants and food containing photosensitive substances such as ash, mustard, rape, spinach, snow lettuce, purple clover, marjoram, buckwheat, lettuce, acacia flowers, amaranth, dragon sprouts, figs, etc.; (4) allergens: such as airborne pollen, dust mites and mold, etc.; (5) certain cosmetics: such as some fragrances, proteins and impure in chemical products Vaseline, etc. to prevent photosensitive skin diseases. Do not sunbathe after contacting or taking the above items.