Retin A or retinoic acid (figure l), is a vitamin A derivative that belongs to a class of chemicals call tretinoins.It was first marketed in 1972 as an acne treatment.At one time,Retin A was available only by prescription but you can now purchase it over the counter. Retin A accel erates the shedding of dead skin cells reduces pore blockage and decreases the oily buildup that usually causes acne.It also dilates blood vessels beneath
the skin and creates new collagen the fibrous protein that gives skin its smooth texture and elasticity.aging and prolonged sun exposure reduce this elasticity,causing wrinkles.