- Alpha Hydroxy Acids,
Alpha hydroxy acids (AHAs) are a group of naturally occurring acids commonly found in certain foods. Because of their abundance in many fruits, alpha hydroxy acids are commonly referred to as fruit acids (citrus acid from citrus fruit, malic acid from apples, tartaric acid from grapes.) Ironically, the two most common alpha hydroxy acids are not found in fruit (glycolic acid from sugar cane juice and lactic acid found predominantly in sour milk.)
Alpha hydroxy acids have been used successfully to treat extremely dry and flaky skin and have been shown to temporarily improve the appearance of photo-aged skin. Many studies have proven AHA’s moisturizing ability (to increase the water content of skin) and have concluded that AHAs enhance the shedding of the most superficial dead skin cells, leaving the skin looking more uniform and feeling smoother and more supple. Some studies claim that AHAs improve the protein structure of the skin that makes up the skin’s strength, but the evidence to support these claims is lacking.
Clinical studies have also shown that the most beneficial effects of AHAs occur at concentrations and at a pH unavailable in over-the-counter (OTC) products. Although OTC moisturizers containing AHAs may be adequate moisturizers, and may temporarily reduce the appearance of fine wrinkles and skin dryness, skin-rejuvenating claims are unproven.
When applied to the skin, skin care products containing AHAs may cause irritation and burning. This may depend on the concentration and pH level of the product; unfortunately, this information is not always available on the product label. It is recommended to use products that identify the concentration of active ingredients. Despite their popularity, and their effectiveness as moisturizers, the exact mechanism of action of alpha hydroxy acids remain unknown. Studies show that AHAs may increase sensitivity to UV radiation. Sunscreen application is advised when using these products.
Vitamin A and its derivatives (retinoids) are possibly the most prevalent anti-aging ingredients on the market today. These derivatives include vitamin alcohol (retinol), vitamin A esters (retinyl palmitate, retinyl acetate), and vitamin A aldehyde (retinal). Retinoic acid (tretinoin), an FDA approved retinoid, is only available by prescription and is NOT found in OTC skincare products. Although retinoid acid is considered the gold standard for photo rejuvenation it is a known dermal irritant and the effects of long-term use are still not known. The indication for use as described by the FDA for one of the most prescribed "anti-wrinkle" prescription creams is as follows: "an adjunctive agent for use in the mitigation of fine facial wrinkles in patients who use comprehensive skin care and sunlight avoidance programs." The package insert clearly states ...DOES NOT ELIMINATE WRINKLES, REPAIR SUN-DAMAGED SKIN, REVERSE PHOTOAGING, or RESTORE MORE YOUTHFUL or YOUNGER SKIN. The weaker derivatives of retinoic acid are commonly found in OTC skincare products. Evidence of the efficacy of these weaker retinoids is much less robust. The majority of studies evaluating the benefits of these OTC retinoids are poorly designed, and the effectiveness of these preparations by most skin experts is regarded as marginal at best. Exposure to sunlight should be avoided when using vitamin A derivatives as their use may increase sun sensitivity and sunburn potential. In addition, Vitamin A derivatives must be avoided during pregnancy as they may increase the risk of birth defects.
Many "age-defying" skincare products on the market contain antioxidants. These products claim to stimulate skin's natural collagen production and diminish the signs of aging. Unfortunately, there is little scientific evidence proving their effectiveness.
What are antioxidants? All living things utilize oxygen to harvest the energy our cells need for survival. Oxygen controls the chemical reactions that break down fats, proteins, and carbohydrates in order to produce that energy. In doing so, oxygen produces an unstable form know as a free radical. Although science has shown that free radical formation is actually an important part of our body's normal function, and in appropriate doses is even good for us (free radical formation increases with exercise), a very popular theory within the scientific community alleges that free radical formation results in cell damage, skin wrinkling, and, perhaps, skin cancer formation. Antioxidants are compounds that donate an electron to the unstable free radicals thereby neutralizing their effects. It's no wonder "antioxidant rich" skincare products containing compounds with green tea, resveratrol, coenzyme Q, and vitamin C, are flying off the shelves.
Antioxidants are very unstable compounds. When exposed to oxygen or light they breakdown, hence the use of opaque bottles and jars. The skin, designed as a barrier to keep things out, does not readily absorb charged molecules, like most antioxidants. Antioxidants applied to the skin surface, if they have not been denatured by the light or oxygen exposure, must penetrate through many layers of skin, into the lower epidermis, and lower into the dermis where the oxidative free radical damage is allegedly occurring. Penetration of these antioxidants must be robust enough, and at a high enough concentration, to have an effect. Unfortunately, there is little, if any, scientific evidence proving this occurs.
Although antioxidants may not be harmful, and may even stabilize the skincare product itself, the benefits of antioxidants in skincare products remains controversial.