Retinoids were one of the first cosmetic ingredients to receive FDA approval to claim the products decrease lines and wrinkles around the eyes. The mechanism of action involves stimulation of new collagen formation as well as elastin production. Other results are thickening of epidermal and granular layers, decreased melanin content, and more compaction of the stratum corneum. In addition, retinoids are effective in the treatment of pre-cancerous moles, thereby delaying the development of melanoma.
Alpha hydroxy acids (AHAs) are derived from the sugars of fruit (glycolic acid) and milk (lactic acid). AHA perform a number of well-documented and desirable function: moisturizing dry sky, cleansing pores, improving skin texture and tone, managing oil-prone skin, and reducing discoloration and age spots. Alpha Hydroxy acids helped shift the balance between the prestige and mass-market sales channels, because this ingredient is inexpensive and moved quickly into mass-market skincare formulas.
By 1996 companies were turning their attention toward enzymes and vitamins. Whereas AHAs exfoliate the skin's top layer of dead cells, enzymes dissolve the dead cells quickly and therefore eliminate the need for a higher concentration of AHAs. Known as "elastase inhibitors," and "collagenase inhibitors," these ingredients slow the action of collagenase and elastase, which, it is said, are responsible for the destruction of collagen and elastin.
Vitamin C and E also gained popularity in the 1990's. Since its discovery in the 1930's, the roles of vitamin C have been numerous. Vitamin C is a water-soluble antioxidant that clenches free radicals and regenerates vitamin E. It's an important regulator of collagen expression stimulating its synthesis.