The use of sunscreen is necessary in cases where the skin needs to be protected from the sun, such as after intense UV rays, after laser skin treatments, after the use of photosensitizing medications, and so on. The main purpose of sunscreen is to prevent sunburn, prevent tanning, and minimize skin irritation caused by UV rays. 1. When the intensity of ultraviolet rays is high, it is easy to burn the skin, which can be manifested as redness or even ulceration of the skin, and it is necessary to use sunscreen when you go out in this case. 2. After skin laser treatment, ultraviolet radiation will make the local skin pigmentation worse, and may even leave pigmentation, so in the period of time after laser treatment, you must pay attention to apply sunscreen when you go out and do a good job of sun protection. 3. After taking drugs with photosensitivity, it is easy to increase the photosensitivity of the organism, which will lead to skin redness, itching, and even skin burns, etc. Therefore, it is necessary to pay attention to sun protection after using tetracycline antibiotics and quinolone antibiotics, and you can choose to put on sunscreen when you go out. Please strictly follow the doctor’s instructions for medication, and do not use medication on your own.