Pimples on the chest belong to acne, the pathogenesis of which has not been fully elucidated, and is related to genetic factors, exuberant secretion of androgens, keratinization of follicular sebaceous gland ducts, propagation of Propionibacterium acnes, emotional factors, and diet. 1. Genetic factors: parents with a history of acne are more likely to have acne in their next generation. 2. Excessive secretion of androgens: Excessive secretion of androgens in the body will cause a large amount of sebum secretion from the hair follicles, which will easily trigger acne. 3. Keratinization of follicular sebaceous gland ducts: Excessive keratinization of follicular sebaceous gland ducts will make it difficult for the secretion to be discharged, which will easily cause acne. 4. Propionibacterium acnes reproduction: The reproduction of Propionibacterium acnes in the hair follicles can easily cause inflammatory reactions, which can also induce acne. 5. Emotional factors: Long-term mental stress, emotional depression, anxiety, etc. may also induce acne. 6. Diet: Eating greasy food and overly sweet products may also cause acne. It is recommended to go to the hospital for a checkup first, to clarify the cause of the disease and follow the doctor’s instructions.