Sun spots will appear on the exposed area after excessive sunlight exposure in summer, which is medically called “solar dermatitis”, caused by the medium-wave ultraviolet radiation of 290-300nm, i.e. sun spot spectrum, which can stimulate the body to produce and release prostaglandins, histamine, 5-hydroxytryptamine, kinins, bradykinin and other inflammatory mediators. Inflammatory mediators may appear on the exposed area, resulting in scarlet spots, obvious edema, and even blisters, blisters, oozing and erosion. When it is hot, the air pressure is low, humidity is high, wind speed is low, sweat gland secretion is hyperactive, glandular pores are in an open state, skin capillaries are dilated, body metabolism is vigorous, coupled with higher air humidity and temperature, it will make sweat unable to evaporate quickly, body heat dissipation is difficult, and it is easy to induce metabolic disorder skin diseases such as solar dermatitis. Sun protection index (SPF) is an important indicator to evaluate the role of sunscreens to prevent sunburn, SPF 8-15 sun spots and tanning phenomenon are inhibited, the value of 15 or more, sun spots and tanning phenomenon is completely inhibited. Therefore, today’s sunscreens require a high SPF, generally between 15 and 30. Studies have shown that the higher the SPF of a sunscreen, the earlier it is used, the more effective the skin’s protection against sunburn. UVA is a component of natural sunlight that has a strong penetrating ability and can penetrate the skin’s surface layer and penetrate deeper into the dermis, destroying collagen and elastin, causing wrinkles and fine lines and sagging skin, which is called photoaging in medical terms. The more the number is added, the better the sun protection effect. Some foods can aggravate the skin photosensitivity, photosensitive food after digestion and absorption, which contains photosensitive substances will enter the skin, if the exposure to bright light at this time, will react with sunlight, and then the skin of the exposed parts of the red, swollen, rash, and accompanied by obvious itching, burning or stinging sensation and other symptoms. Common photosensitive foods are cabbage, amaranth, capers, radish leaves, rape, mustard, beets, marjoram, spinach, amaranth, lettuce, buckwheat, acacia, fungus, figs, snails, shrimp, crabs, mussels, algae and so on. There are also some sitting in the office of white-collar workers should also pay attention to, some office buildings are floor-to-ceiling transparent glass, some people think that sitting indoors will not sunburn, but in fact light will be refracted through the glass, if you sit on the glass side of the location for a long time, may also cause solar dermatitis. It is worth noting that some clinically used drugs also carry some photosensitivity, such as sulfonamides, tetracyclines, salicylates, certain antitumor and diuretic drugs, etc. Patients are best to consult with the relevant dermatologist before taking them. If the skin already has erythema, blisters, vesicles and other symptoms need to promptly seek medical attention.