AHA! Investigators discover another source of sunburn
First posted June 12, 2003
Trying to delicately scrape away those fine lines? Or just moisturizing your dry skin during hot summer days? If you're using certain products to do the job, you may be doing your skin an injustice.
Topical glycolic acid, a type of alpha-hydroxy acid (AHA), is used in many cosmetic cleansers to lessen fine wrinkles and in some lotions and shampoos for dry skin. But the very ingredient that soothes away the wrinkles also may make you more susceptible to them, say researchers at Ivy Laboratories in Philadelphia.
For areas of skin with psoriasis, the AHAs instead may make the skin more receptive to sun exposure or phototherapy, says Steve Feldman, M.D., Ph.D., professor of dermatology, pathology and public health sciences at Wake Forest University School of Medicine in Winston-Salem, N.C.
In a study recently published in the journal Photodermatology, Photoimmunology and Photomedicine, the Ivy Laboratories investigators found that AHAs made the skin more sensitive to the damaging effects of ultraviolet light, confirming previous studies. The researchers studied 29 volunteers by applying either 10 percent glycolic acid or placebo (inactive substance) to their backs. After six daily applications for four weeks, the volunteers were exposed to 1.5 times the minimal amount of ultraviolet light that induces sunburn (called the "minimum erythemal dose" or MED).
The areas with glycolic acid were significantly more sun-sensitive than those with placebo. The study also found a correlation between the use of AHAs and an increase in the number of "sunburn" cells formed in the skin. Sunburn cells are skin cells that become damaged by UVB light and, because of the damage, are eliminated from the body. One week after stopping the acid application, the number of sunburn cells returned to the same level as the placebo group.
According to Alan Bennett, public affairs spokesperson for the U.S. Food and Drug Administration (FDA), the skin damage results from peeling off the top layer of skin, and exposing "newer" skin to the UVB rays. The FDA has examined the effect of UVB on AHA-affected skin, and recommends that individuals use home products containing 10 percent or less of AHA.
In December 2002, the FDA issued a recommendation for a "sunburn alert" label stating the products with AHA "may increase your skin's sensitivity to the sun and particularly the possibility of sunburn. Use a sunscreen and limit sun exposure while using this product and for a week afterwards."
Dr. Feldman agrees. "Since the normal skin doesn't need any more sun/UV damage than it already has," he says, "using a sunscreen on skin treated with AHAs seems to make good sense."
Some products, such as night creams and moisturizers, contain both AHAs and sunscreen. The FDA says that the SPF may help counter increased skin sensitivity to UV radiation.
Where are the AHAs?
To find out if a cosmetic contains an AHA, look on the list of ingredients on the outer packaging. AHA ingredients may be listed as:
- glycolic acid
- lactic acid
- malic acid
- citric acid
- glycolic acid + ammonium glycolate
- alpha-hydroxyethanoic acid + ammonium alpha-hydroxyethanoate
- alpha-hydroxyoctanoic acid
- alpha-hydroxycaprylic acid
- hydroxycaprylic acid
- mixed fruit acid
- tri-alpha hydroxy fruit acids
- triple fruit acid
- sugar cane extract
- alpha hydroxy and botanical complex
- L-alpha hydroxy acid
- glycomer in crosslinked fatty acids alpha nutrium (three AHAs).
Of these, the most frequently used in cosmetics are glycolic acid and lactic acid.
For more information, go to the FDA draft labeling guide on AHA products:
http://www.cfsan.fda.gov/~dms/ahaguide.html
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