Acne is commonly known as acne, and hairline acne may be caused by factors such as the skin in the hairline area not being easily cleaned, dietary habits, changes in hormone levels, mental and immune factors. Acne is a common skin disease that manifests itself as chronic or recurrent papules, pustules or nodules on the face, neck, trunk or proximal upper limbs and hairline. The following factors may be associated with hairline acne. 1. Skin in the hairline area is not easy to clean: Since the skin in the hairline area is not easy to clean, dirt and oil can easily clog the pores. 2. Dietary habits: after eating spicy and irritating foods, it is easy to cause hairline acne. 3. Higher androgen levels during puberty: this can lead to increased sebum secretion from localized hair follicles and promote acne. 4. Mental factors or immune abnormalities: the presence of stress, anxiety or decreased immunity may also lead to hairline acne. If the above symptoms continue to remain unrelieved, you should go to the hospital in time for symptomatic treatment under the guidance of your doctor.