From what you are describing it sounds like a type of folliculitis or infected hair follicle. Folliculitis is often caused by the Staphylococcus aureus (staph) bacteria. Although staph bacteria live on your skin all the time, they generally cause problems only when they enter your body through a cut or other wound. This can occur through shaving or with an injury to the skin such as infected hair follicle. Generally speaking, tight underwear, friction from sitting long periods of time, use of hot tubs or hot baths, dermatitis, obesity, hot weather, diabetes, and certain medical conditions can all lead to folliculitis. Normally, folliculitis does not require treatment unless it reoccurs (as yours has) or if the lesions become red, warm to the touch, and swollen/ooze. Antibiotics are often prescribed in this case and also a topical cream to help keep the breakouts down to a minimum.
The nape of the neck, groin, and underarm is a likely place for Folliculitis to occur.
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If the area is bothering you, you will need to have it incised and drained. If it begins to ooze or is warm to the touch, or becomes painful, you will also need to have it checked.
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