An antibiotic is called clindamycin. It restricts the development of acne-causing bacteria as well as the irritation these bacteria generate. Tretinoin causes proper shedding of the skin cells that block the hair follicles in acne-prone areas and normalizes the proliferation of superficial skin cells. By doing so, you can stop sebum from accumulating and early acne lesions (such blackheads and whiteheads) from developing.