Acne vulgaris is a medical term for common acne, which may be caused by increased androgen levels, bacterial infections and hyperkeratosis of hair follicles. 1. Increased androgen levels: Increased levels of androgens in the body may trigger the sebaceous glands to secrete large amounts of sebum, thus triggering acne vulgaris. 2. Bacterial infection: The most common bacterial infection is Propionibacterium acnes, which can easily trigger inflammatory acne if it proliferates locally. 3. Hyperkeratosis of hair follicles: This can lead to a narrow opening of the follicle canal, where excess sebum builds up and can’t be discharged from the body properly, thus forming acne pimples that are visible to the naked eye. There are many causes of acne vulgaris, and patients are advised to consult a doctor at a regular hospital to learn more about this issue.