Legs were bitten by insects, red and swollen is belong to the insect bite dermatitis, can be adjusted through general treatment, topical drugs, oral medication and other measures. 1. General treatment: first of all, you should wash with water, avoid scratching, avoid hot water scalding, local cold compress can reduce edema, relieve itching. 2. Topical medication: you can use glycerine lotion to relieve itching, but also with glucocorticoid ointment, such as dexamethasone ointment, tretinoin cream and so on. 3. Oral medication: patients with large swelling and itching can take antihistamines such as loratadine and cetirizine, and severe cases can be combined with glucocorticosteroid medication, such as prednisone tablets and dexamethasone tablets. Insect bite dermatitis is recommended to first go to the hospital to check, identify the cause, under the guidance of the doctor with medication.