Purple bumps on one side of the buttocks may be due to folliculitis, sebaceous cysts and ringworm. 1. Folliculitis: the most common reason for purple bumps on one side of the buttocks is folliculitis, due to sedentary reasons leading to the buttocks local permeability is not good, the skin is prone to folliculitis, mostly manifested as red, purple or even purple pimples and pustules. 2. Sebaceous cysts: sebaceous cysts are due to the sebaceous gland secretion function, sebum can not be normally discharged from the follicle mouth in the gland accumulation, the formation of cysts, small cysts can be asymptomatic, large cysts can be manifested as a skin bulge, and the combination of infections will be red, swollen and even purple. 3. Ringworm: purple buttocks bumps may be due to ringworm, long-term sitting and standing after the buttocks are not ventilated, increasing the chance of fungal infection, initially manifested as red pimples, pustules and purple bumps will appear in severe cases. If the patient’s buttocks side of the purple pimples, you need to timely to the hospital, according to the doctor’s advice to carry out the appropriate examination to clarify the cause of the active treatment.