If you have a pimple on the back of the neck under the hair, it is possible that the area has folliculitis, because the hair follicles in this area are more developed, once the infection of conditional pathogenic bacteria or immune system decline, it will certainly lead to local inflammation. It is possible that the patient’s personal hygiene may be a problem, as the local cleanliness is not ideal, which may cause the growth of bacteria, resulting in local inflammation. Of course, it is also possible that there is a cyst in the area, especially a sebaceous cyst, which, if it does not subside for a long time, may cause a local bacterial infection and eventually form a canker sore in the area, and if the canker sore continues to expand, it may form a local reaction such as an abscess. It is possible that folliculitis formed by the original fungal infection in the area, especially Malassezia folliculitis formed after Malassezia infection, may also appear as a reaction to acne in the area.