Forehead acne may be caused by folliculitis, acne, prickly heat and so on. 1. Folliculitis: Most of the forehead skin is damaged due to bad habits and lack of attention to personal hygiene, causing repeated infections by Staphylococcus aureus, which results in red papules centered on hair follicles, with white pustules at the top of some of them. 2. Acne: When in a state of high hormone level and large amount of sebum secretion, abnormal keratinization of the cells around the hair follicles will affect sebum discharge, and the large amount of sebum will lead to over proliferation of Propionibacterium acnes, which will cause inflammatory reactions. It can also be triggered by stress or the consumption of high-sugar or high-oil foods. 3. Prickly heat: Prickly heat is a superficial skin disease that occurs in a hot environment. If the hair in the forehead area is long, this situation is not conducive to washing and heat dissipation, and sweat cannot be discharged normally, which will lead to prickly heat. There are many other diseases that may cause forehead acne, it is recommended that patients seek medical attention to identify the cause and follow the doctor’s instructions for targeted treatment.