What are the dangers of glycolic acid?

Often used in chemical peels, glycolic acid is a fruit acid known for its exfoliating properties. Indeed, it has the ability to detach dead skin cells on the surface, thereby stimulating the renewal of the epidermal cells. Glycolic acid is present in many cosmetic product formulas at a concentration between 4 and 10%: serum, cream, tonic lotion, shower gel, etc... However, although it is suitable for almost all skin types (normal, combination to oily, and mature), glycolic acid can sometimes be poorly tolerated. The effects of this active ingredient vary greatly and depend on the concentration of glycolic acid, the pH of the product, and the application time. That's why it's important to always thoroughly read the instructions before any application.

Thus, it is likely and normal to experience slight tingling and a mild warming sensation, and to see redness appear following the application of cosmetics containing glycolic acid. However, depending on your skin's tolerance level, these symptoms can intensify and may even be accompanied by erythema, burning sensations, tightness, itching, and facial swelling, and hyperpigmentation. In rare cases, hypopigmentation, persistent erythema, and acne flare-ups have been reported. Upon the onset of such side effects, immediately stop using the product and consider thoroughly rinsing your face with water. However, at Typology, we advise against its use onsensitive and reactive skin, as well as for individuals suffering from an inflammatory skin condition (eczema, rosacea, herpes, etc…). It is also advisable to avoid using it in pregnant women. Indeed, it is the cause of vascular disorders related to hormonal impregnation, resulting in congestive flare-ups on the face: the skin reddens more easily and becomes more sensitive.

Like other fruit acids found in most facial care products, glycolic acid does not mix well with the sun. Indeed, it can increase the skin's sensitivity to the sun's UV rays and raise the risk of sunburn even without direct sun exposure. Due to its exfoliating power, the skin is left without its natural protection against the sun's rays until the complete reformation of the stratum corneum and the hydrolipidic film. Indeed, the stratum corneum helps protect the dermis by absorbing or reflecting UV rays, particularly UVB rays. However, by thinning this protective layer, we expose our epidermis to cellular damage: the skin begins to redden under the effect of UV rays. That's why it's better to apply your glycolic acid treatments in the evening, especially since our cell renewal process is more active at night. If you're using glycolic acid-based products, make sure to properly hydrate your skin with a moisturizing face cream suitable for your skin type, to restore the hydrolipidic film. Moreover, remember to protect your skin from the sun by applying a SPF30 type photoprotection in the morning.

Furthermore, to avoid any adverse effects, perform a sensitivity test beforehand in the crook of your elbow for 48 hours with the product before using it on your face, and also avoid applying it around the eye area. If your skin begins to sting and/or turn red, reduce the acid concentration and/or space out the applications. For instance, you can start by using a product with a low concentration of glycolic acid and space out the applications to once a week in the case of highly concentrated treatments to allow your skin to get accustomed to the active ingredient, and thus see how your skin reacts. Subsequently, you can gradually increase the application frequency and concentration over time.

It's important to know that the combination of glycolic acid with other cosmetic actives can be irritating. This is particularly the case with the combination of glycolic acid and those based onretinoic acid (vitamin A). Although this combination has shown interesting results on the skin, it is not recommended for dry and sensitive skin types that may not tolerate it well due to its strong effect, especially if your skin is not accustomed to retinol.

The same applies tosalicylic acid (B.H.A.). It is particularly important to pay attention to the overall concentration of keratolytic ingredients. Therefore, we advise you to consult with your dermatologist beforehand, who will be able to provide the best advice and find the right dosage based on your skin and your needs. However, salicylic acid and glycolic acid can be effectively combined as localized treatments for acne.

Similarly, we advise against combiningglycolic acid with alkalizing agents such as vitamin C. Indeed, for optimal effectiveness, glycolic acid should be in formulas with a slightly acidic pH (between 3 and 5.5), and vitamin C, for instance, will lose its effectiveness in this combination. Likewise, the combination of glycolic acid with clay masks is incompatible. Indeed, incorporating it with clay, which is rather alkaline in nature, while glycolic acid is an acidic active ingredient, is not recommended and will impact the latter's effectiveness. Also, avoid using vitamin B3 with glycolic acid. The same observation applies, vitamin B3 requires a neutral pH to function effectively, while glycolic acid has a low pH.

• KORNHAUSERA. & al. Topical application of glycolic acid intensifies photodamage caused by ultraviolet light. Photodermatology, Photoimmunology and Photomedicine (2003).

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