Pimples, or acne. The recurrence of acne on the forehead and chin may be due to insufficient local skin cleansing, endocrine disorders, improper diet, improper use of cosmetics and other factors that lead to clogging of hair follicles, which in turn leads to localized infections and inflammation. 1. Inadequate local skin cleansing: The forehead and chin are areas where sebaceous glands are well distributed, and the increased secretion of sebaceous glands leads to blockage of pores, which in turn leads to bacterial infections and the formation of acne. 2. Endocrine disorders: After puberty, androgen activity is higher, stimulating the sebaceous glands on the chin and forehead to secrete more sebum, which is most common in adolescent males and females. 3. Improper diet: Eating too much spicy, greasy food and sweets can cause increased sebum secretion. 4. Improper use of cosmetics: Excessive use of cosmetics can lead to clogged pores, secondary bacterial infections and acne. For those with recurring acne on the forehead and chin, it is recommended to consult a dermatologist at a regular hospital to clarify the cause and then provide targeted treatment.