Buttock red a grain of very itchy for several reasons: 1, there may be related to insect bites, the so-called insect bite dermatitis, pay attention to their habits, living hygiene, do symptomatic treatment, such as oral antihistamines, topical antiallergic drugs, etc. 2, may be eczema, will also be manifested as a red papule, but also itchy, especially in the night is more itchy, so it is necessary to go to the hospital to do the examination, to the doctor to see if eczema. 3, may be a fungal infection, may be annular erythema, also surrounded by red pimples, can also be manifested as red and a grain of a grain. Is not eczema, if it is eczema should do symptomatic treatment. 3, may be fungal infection, may be annular erythema, surrounded by red pimples, can also be manifested as a red and a grain of red, if it is a fungal infection can be used antifungal drugs, of course, we must first do a test to determine whether it is a fungal infection.