Pustules on the back may be caused by acne, folliculitis and other diseases. 1. Acne: Acne is clinically characterized by pustules, papules and comedones, and is commonly found in areas with dense sebaceous glands, including the head, face, chest and back. Acne is a multifactorial disease, and its pathogenic factors include abnormal androgen levels, inflammation, and abnormal keratinization of follicular sebaceous gland ducts. 2. Folliculitis: The mechanism of folliculitis is related to the infection of hair follicles by pathogenic bacteria. Folliculitis on the back can be seen in the infection of Staphylococcus aureus and Malassezia, and it can be triggered by factors such as obesity and excessive sweating. Folliculitis usually manifests as red papules or pustules, and the disease often occurs on the head and face, neck and shoulders, chest and back. There are more causes of pustules on the back, and patients are advised to go to regular hospitals to clarify the cause of the disease.