Is Glycolic Acid Something to Avoid in the Sun?

Glycolic acid, derived from sugarcane, is a small molecule that penetrates the skin easily. It works by breaking down the bonds between dead skin cells, promoting exfoliation and revealing smoother, brighter skin. While it’s effective for improving texture and hyperpigmentation, glycolic acid may increase the skin's sensitivity to ultraviolet (UV) light.

Studies show that glycolic acid can indeed enhance the skin's photosensitivity. One pivotal study by KORNHAUSER A. & al. (2003) applied 10% glycolic acid (pH 3.5) to the backs of 29 Caucasian subjects. After four weeks of daily application, the treated skin was exposed to UV light. The study revealed that areas treated with glycolic acid showed increased sensitivity to UV light, indicated by a higher number of sunburn cells (SBCs) and a lower minimal erythema dose (MED), which is the smallest dose of UV radiation required to cause visible redness or erythema (sunburn) on the skin.

Interestingly, while cyclobutyl pyrimidine dimers (CPDs) in DNA—markers of UV-induced damage—were elevated, they were not statistically significant. This suggests that glycolic acid enhances superficial damage (like erythema and SBCs) but may not significantly affect deeper DNA damage in this context.

The good news is that this photosensitizing effect seems to be temporary. The same study observed that discontinuing glycolic acid use for a week allowed the skin’s sensitivity levels to return to normal. This implies that with proper timing and protection, glycolic acid use does not have long-lasting photosensitizing effects.

The exact mechanism by which glycolic acid increases photosensitivity is not fully understood. Unlike chemical sunscreens, glycolic acid does not absorb UV radiation directly. Research suggests that its photosensitizing effect could stem from its ability to exfoliate and thin the stratum corneum, the skin’s outermost layer. By removing this protective layer, glycolic acid might make the skin more susceptible to UV penetration.

A report by ANDERSEN F. A. (1998) corroborates this, highlighting that glycolic acid's exfoliating action can expose the skin to increased UV radiation damage. This effect aligns with the findings from HONG J. T. & al. (2002), who noted enhanced skin damage when glycolic acid was used alongside UVB exposure. However, HONG’s study also found that this enhancement occurred without increasing inflammation markers like PGE2 or COX-2, indicating a specific interaction at the epidermal level rather than deeper inflammatory processes.

Interestingly, the study also investigated salicylic acid, another popular exfoliant. Despite its exfoliating properties, salicylic acid did not show the same photosensitizing effects as glycolic acid. This suggests that the mechanism behind glycolic acid’s photosensitizing effect remains theoretical, and further research is needed to fully understand why glycolic acid increases sun sensitivity.

Given these findings, it is advisable to exercise caution when using glycolic acid products if you plan to be exposed to sunlight. Here are some key recommendations:

• Cover the Treated Area: Whenever possible, cover the area where glycolic acid was applied. If it's the face, try to avoid direct sunlight and consider wearing a hat or using other physical barriers for added protection.

• Use Sunscreen: Always apply a broad-spectrum sunscreen with a high SPF when using glycolic acid. Sunscreen can help mitigate the increased risk of sunburn and UV-induced damage.

• Timing Matters: To minimize risks, apply glycolic acid products in the evening. This reduces the likelihood of immediate sun exposure after application. For those with frequent sun exposure, reducing the use of glycolic acid or switching to less photosensitizing alternatives might be advisable during summer months.

• Monitor Your Skin: If you experience redness or irritation, it might be best to pause glycolic acid use or reduce the frequency of application, especially if you are exposed to the sun regularly.

Glycolic acid is a powerful skincare ingredient with numerous benefits, but it requires careful handling, especially concerning sun exposure. Even at low concentrations (e.g., 5%), glycolic acid can still increase photosensitivity due to its exfoliating effects, though to a lesser extent than higher concentrations. Research indicates that it can enhance sensitivity to UV radiation, causing sunburn cells and erythema. However, with proper precautions like sunscreen use and timing, you can still enjoy its benefits while minimizing risks.

• ANDERSEN F. A. Final report on the safety assessment of glycolic acid, ammonium, calcium, potassium, and sodium glycolates, methyl, ethyl, propyl, and butyl glycolates, and lactic acid, ammonium, calcium, potassium, sodium, and tea-lactates, methyl, ethyl, isopropyl, and butyl lactates, and lauryl, myristyl, and cetyl lactates. International Journal of Toxicology (1998).

• HONG J. T. & al. Effect of glycolic acid on UVB-induced skin damage and inflammation in guinea pigs. Skin Pharmacology and Applied Skin Physiology (2002).

• KORNHAUSER A. & al. Topical glycolic acid enhances photodamage by ultraviolet light. Photodermatology, Photoimmunology & Photomedicine (2003).

• HEARING V. J. & al. The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage, and sunburn cell formation in human skin. Journal of Dermatological Science (2009).

• SHARAD J. Glycolic acid peel therapy – A current review. Clinical, Cosmetic and Investigational Dermatology (2013).