The darkening of a child’s leg sockets may be caused by a long-term lack of cleaning, acanthosis nigricans, excessive fat accumulation and other factors. 1. Long-term cleaning is not in place: Long-term cleaning is not in place, resulting in the accumulation of dirt, resulting in the darkening of the leg sockets, pay more attention to daily cleaning, and develop good hygiene habits. 2. Acanthosis nigricans: Acanthosis nigricans, also known as acanthosis nigricans or pigmented papillary dystrophy, is a skin disease characterized by deepening of skin color and papillary or velvety hyperplasia. It mostly occurs in skin folds, such as the neck, armpits, groin and popliteal fossa. The first step should be to actively search for the cause of the disease. For patients with malignant acanthosis nigricans, visceral tumors must be actively searched for and surgically removed. For obese acanthosis nigricans, obesity must be corrected, and with weight loss, acanthosis nigricans is cured. For drug-induced patients, all suspected pathogenic drugs should be stopped in time, and the rash can be cured after stopping the drugs. 3. Excessive fat accumulation: if the baby is fat, the subcutaneous fat accumulation in the leg pit is more, and the thigh root is subjected to friction and stimulation for a long time, it can be proliferated and aggravated, resulting in the surface becoming black. Causes of inner thigh black color is more reasons (such as chronic simple moss post-inflammatory hyperpigmentation), it is recommended to pay attention to local cleanliness and hygiene, if necessary, go to the hospital dermatology department to find out whether it is related to pathological factors, it is recommended to give treatment for the cause of the disease.