A small pustule at the corner of the mouth may be related to localized skin breakdown, bacterial infection and sebaceous gland secretion. 1. Localized skin breakdown: when the skin at the corner of the mouth breaks down with small wounds due to a variety of reasons, it is easy to induce bacterial infection, thus causing the problem of a small pustule growing at the corner of the mouth. 2. Bacterial infection: Bacterial infection may lead to inflammation of the local hair follicles, due to the stimulation of the inflammation, thus causing the corner of the mouth to grow a small pustule performance. 3. Sebaceous gland secretion: the corner of the mouth long pus may be associated with sebum secretion, excessive oil secretion, easy to block the hair follicles, causing the occurrence of folliculitis, thus appearing in the corner of the mouth long a small pus performance. There are many other reasons that can lead to the phenomenon of a small pustule at the corner of the mouth, it is recommended that such patients go to the regular hospital, complete the relevant examination, clear causes under the guidance of the doctor symptomatic treatment, and actively deal with.