The causes of swollen and painful skin on the surface of the foot are mainly the following: 1, insect bite dermatitis: the skin of the foot is an exposed part, but also the part of the mosquitoes often bite, especially children in mosquito bites, local redness and swelling is more obvious. The local treatment is mainly anti-allergy treatment, which can be done by applying topical stove glycolic lotion or with oral antihistamine syrup, such as loratadine syrup. 2. Infectious diseases of the skin on the foot surface: clinically it is common to have tinea pedis infection, i.e. the patient has tinea pedis. Because of itching or erosion of tinea pedis, frequent rubbing, irritation, and scratching lead to secondary infection of the skin on the back of the foot by fungi, bacteria, or broken epidermal cells that enter the skin through the broken skin. Clinical manifestations are redness, swelling and pain, and even the formation of localized dermatophytosis; 3. Other causes: inflammatory diseases of the bones and joints of the foot, trauma to the skin of the foot surface. Patients with swelling and pain on the top of the foot should go to the dermatology department of the hospital, where a detailed examination by a dermatologist will clarify the diagnosis and give the correct treatment.