Erythromycin ointment is not strictly used to clear acne, but mainly to treat co-infected acne, also known as acne vulgaris. Erythromycin is an antibacterial drug, and topical application of this antibacterial drug is not required for mild acne, but in the case of moderate to severe acne, a combination of topical antibacterial drugs is required. The main pathogenic bacteria that aggravate acne infection is Acinetobacter. The proliferation of this bacteria can induce and aggravate the inflammatory response, and erythromycin can be very effective in killing this bacteria. However, the occurrence of acne is not only an infection, there are other triggers such as excessive sebum production, blockage of sebaceous ducts in the hair follicles, and inflammatory reactions, so it is usually necessary to combine other medications such as vitamin A. For more severe acne such as nodules or bulbous acne, oral antibacterial medications may also be required.