Pimple pus at the anal opening may be caused by perianal abscess, folliculitis, sebaceous cysts and other diseases. 1. Perianal abscess: usually due to anal gland obstruction, diabetes mellitus and other factors, leading to acute suppurative infection of the rectal anal canal and the surrounding soft tissues, resulting in the phenomenon of pimples and pus at the anal opening. 2. Folliculitis: this disease can occur in any hair follicle part of the body, the etiology of this disease is not clear, may be related to mite parasites, bacteria, fungi and other pathogens infection and other factors, due to inflammatory media stimulation, may lead to the patient to appear anal pimples pus phenomenon. 3. Sebaceous cysts: usually caused by sebaceous gland excretory duct obstruction and other factors leading to the accumulation of glandular contents, if infection occurs, it may lead to patients with pimples and pus at the anal opening. When patients have pimples and pus at the anal opening, they should go to the hospital in time for examination and treatment under the guidance of the doctor to avoid delaying the condition and leading to adverse consequences.