Acne on the back of the neck may be a result of folliculitis of the skin behind the neck, or localized acne vulgaris due to blockage of the follicular sebaceous openings. When acne vulgaris is secondary to infection by conditional pathogens, especially Propionibacterium acnes or Staphylococcus aureus, a certain inflammatory reaction may occur, manifesting as localized papules of follicular consistency, accompanied by redness and swelling, and some may be accompanied by a certain purulent manifestation, manifesting as pustules, etc. So acne on the back of the neck is actually a local infection of the hair follicles, or sebaceous glands. For these infections, active treatment with antibiotics is needed.