A grain of bumps on the buttocks may be caused by bad habits or perifollicular keratosis, folliculitis, the specific causes and the way the bumps are formed are as follows: 1, bad habits: due to work reasons need to be often sedentary, resulting in serious skin friction, then a grain of bumps can appear on the buttocks; 2, folliculitis: mainly appear folliculitis papules, acne or pustules, there may be itching, stinging pain. Stinging sensation, can be treated with topical fusidic acid ointment, adapalene gel, etc.; 3, perifollicular keratosis: a single rash is a pinpoint-sized follicular papule, dark red, brown or skin-colored, with a gray-brown or gray-white corneal plug at the tip of the rash, in which a fine hair sticks out or curls up. After peeling off the plugs, tiny depressed pits are left at the tip, and new plugs soon grow out. The rash occurs at the mouth of each hair follicle, does not fuse with each other, persistent and scattered distribution, clusters and clusters, chicken skin-like appearance, erythema around the hair follicle, serious small pustules, heavy in winter and light in summer, no conscious symptoms.