Retinoid is the general category name for any and all forms of vitamin A. Tretinoin is a form of vitamin A and, therefore, comes under the general heading of retinoids. The best-known products that contain tretinoins are Retin-A, Renova, Retin-A Micro, Tazorac, Avita, and generic tretinoin. These are all basic treatments for blemishes because they change the way skin cells are formed in the layers of skin as well as in the pore. If skin cells have an abnormal shape, they tend to stick together and shed poorly, often getting backed up in the pore. Tretinoin can transform cell production by improving shedding and by unclogging pores, thereby producing a significant reduction in inflammatory lesions. Topical tretinoins and antibacterial agents have complementary actions and they work well together, but their application must be separated, at least if the antibacterial agent you’re using is benzoyl peroxide. Benzoyl peroxide can render tretinoin ineffective when the two are applied together. The solution is to use benzoyl peroxide in the morning and your tretinoin product at night. Tretinoins are not able to kill P acnes, the bacteria that cause the breakouts, but an antibacterial agent can. Meanwhile, tretinoins can improve and restore the shape of the pore, opening a clear pathway for the antibacterial agent so it can be more active. (Sources: American Journal of Clinical Dermatology, June 2008, pages 369-381; Clinical Therapy, June 2007, pages 1086-1097; and Journal of the European Academy of Dermatology and Venereology, December 2001, page 43.)
One of the major drawbacks to the use of tretinoin is the irritation it can cause. For some people this can be so severe as to prevent its use. But there are alternatives. There is a great deal of research showing that adapalene (brand name Differin), another retinoid but different from tretinoin, can be just as effective as tretinoin but without the irritation (see the following section on Differin).
Meanwhile, remember that using any tretinoin product can make the skin more vulnerable to sun damage and sunburn. It is essential to wear an SPF 15 sunscreen that contains the UVA-protecting ingredients avobenzone (butyl methoxydibenzylmethane), Mexoryl SX (ecamsule), Tinosorb, titanium dioxide, or zinc oxide as the active ingredient. Zinc oxide and titanium dioxide are occlusive and can possibly clog pores, and synthetic sunscreen ingredients can be sensitizing for some skin types, so it may take experimentation to find the right sunscreen that works best for your skin type.