Sun spots are oval or smooth on the skin, and the color is dark brown spots or light brown. Generally, it is easy to appear on the outside of the forearm, the back of the hand, the front side of the calf and the face, and it is generally the size of rice grains to the size of pentagonal coins. Before sunburn forms on the skin, it will first cause pain, itching and peeling, and then it will form spots.
The formation of sunburn is caused by sun exposure, not congenital or pathological spots. Therefore, in treatment, sunburn can be effectively solved by external application.
Extended data:
Sunburn, also known as sun spot, is oval or smooth and dark brown, which is common on the outside of forearm, back of hand, front of calf and face. Professor Wang Zhihong from the Department of Dermatology of Peking Union Medical College Hospital introduced that sunspots refer to brown or black spots on the skin or mucous membrane, which can occur in any part of the skin, or at the junction of the skin and mucous membrane or the conjunctiva of the eyes. The diameter is often less than 5mm, the boundary is clear, the surface is smooth or slightly peeled, sporadic, single or multiple, but not fused.
Melanocytes are located in the basal layer of epidermis. The growth, proliferation and differentiation of melanocytes are very complicated, which are influenced by race, ultraviolet, age, hormones, cytokines and other factors, so that different races, environments and ages show different skin colors.
Moreover, the abnormal function and structure of melanocytes will reduce and increase the pigment of the skin, and some diseases such as vitiligo, freckles, pigmented nevus and other common skin diseases will appear. Melanin is the main pigment that determines skin color. Its physiological function is to protect tissues and prevent damage caused by ultraviolet rays, such as sunburn, aging and cancer.
When the skin is damaged by ultraviolet rays, melanin begins to secrete to protect the skin, and tyrosinase also increases secretion, so that more melanin can be formed, and melanocytes are transformed into another substance called dopa under the action of tyrosinase. Dopa is the precursor of all spots.
Dopa is oxidized to form real melanin, which enters the skin surface with metabolism and finally peels off with aging keratin. If metabolism is not smooth, pigmentation will gather locally, and skin color will deepen or form spots.
Sunburn is not only related to sun exposure, but also related to age, and generally does not fade by itself. Physical peeling method refers to the application of tretinoin or salicylic acid ointment on the sunburn site to promote the peeling of the skin surface, thus achieving the effect of freckle removal and whitening. But this method can't be done overnight, it needs a long-term process, and it is not suitable for sunburn with darker skin color.
References:
People's Network-There is a "law" to eliminate sunburn.