Everything you need to know about glycolic acid.

Glycolic acid is the smallest organic acid of the alpha-hydroxy acids (A.H.A.), also known as fruit acid alongside lactic acid and citric acid. Derived from cane sugar, beetroot or grapes, glycolic acid has established itself as the top active ingredient for chemical peels due to its exfoliating strength, meaning it effectively detaches dead cells on the skin surface, thereby boosting cellular renewal. Moreover, it stands out from other A.H.A.s due to its reduced molecular size, giving it an excellent ability to penetrate the skin for deep action. Acne, wrinkles, hyperpigmentation, lack of radiance, scars: glycolic acid can also address these issues. It's no surprise that it's formulated in creams, lotions, serums or as a peeling solution. Glycolic acid is also used to stabilise the pH of cosmetics.

Glycolic acid is a true ally in maintaining and promoting a healthy epidermis. Indeed, this active ingredient has multiple benefits, acting at all levels to smooth out irregularities. Glycolic acid is particularly renowned for its keratolytic effect. It helps to shed dead cells on the surface. The non-abrasive chemical action of glycolic acid breaks the bonds that hold dead skin, thus ensuring effective and gentle exfoliation. This controlled desquamation thus activates cellular renewal to the benefit of:

• The appearance of the skin:

  Renowned for its exfoliating power, glycolic acid helps to regulate sebum production in oily skin and thus inhibit the formation of blemishes, caused by pore obstruction from dead cells, which leads to the emergence of blackheads and acne. As such, with pores being unclogged and less dilated, spots and blackheads become less frequent. Moreover, this active ingredient helps to reduce acne scars thanks to its exfoliating action, promoting cell renewal. Consequently, these skin irregularities are diminished. Thus, glycolic acid promotes skin texture uniformity and helps to restore smooth skin.

• The Complexion:

  Thanks to its peeling effect, glycolic acid effectively removes dead, dull, and dehydrated cells from the surface of the epidermis. This exfoliating action allows healthy cells to emerge (cell renewal), which restores radiance and luminosity to the face. It can also reduce hyperpigmentation. Indeed, depending on the concentration of glycolic acid, exfoliation can rid the skin of melanin-rich skin cells on the surface. This phenomenon can even trigger cell renewal at the basal layer of the skin, the deep layer of the epidermis, where the melanocytes, the melanin-producing cells, are located. This therefore allows the reduction of brown spots caused by age or sun exposure (including melasma) and thus lightens the complexion. It also contributes to the synthesis of hyaluronic acid and provides a hydrating effect to the horny layer of the skin. Result: the epidermis regains its firmness and the complexion its radiance, and the skin is plumped, softer and smoother.

• Skin ageing:

  Glycolic acid also operates on several levels to combat the signs of skin ageing, in addition to its depigmenting action against brown spots, caused by an accumulation of melanin, which can appear with age. Indeed, glycolic acid can penetrate as far as the dermis. In this context, it can stimulate the synthesis of collagen and elastin, which weakens with age, responsible for the firmness and elasticity of the skin, and also the production of hyaluronic acid, a natural humectant responsible for skin hydration, which tends to gradually decrease with age. Thus, glycolic acid helps the skin to maintain a good level of hydration, to firm up and tone, but also to fade wrinkles and fine lines.

Glycolic acid has also demonstrated its effectiveness in hair care, particularly for dry, dull, and oily hair. Indeed, due to its small molecular size, glycolic acid rapidly penetrates the hair surface to hydrate and revitalise it, thereby improving hair resilience by reducing breakage and enhancing hair shine. In cases of dandruff, its exfoliating action allows for a deep cleanse of the scalp, facilitating the removal of flakes. This helps to reduce flaking and strengthen the scalp. Glycolic acid also aids in eliminating excess sebum, a problem encountered by oily hair.

Glycolic acid is present in a large number of cosmetic products (serum, lotion, cream, mask, shampoo, etc..) and aesthetic treatments (chemical peel). However, not all glycolic acid treatments are created equal. Its effectiveness depends on two factors: its concentration and the overall pH in the formula. In cosmetic products, its concentration varies between 4 and 10% depending on the needs of the skin and will allow for anything from gentle exfoliation to more pronounced skin peeling.

A concentration of 4% is sufficient to provide a moisturising effect. These types of products can also be beneficial in preparing the skin to better tolerate subsequent treatments with higher concentrations of glycolic acid by acidifying the stratum corneum. Around 8 to 10%, the treatments, suitable for night-time application, begin to have a keratolytic effect similar to a mild peel, thus stimulating the renewal of skin cells. These formulations also help to combat skin irregularities (excess sebum, enlarged pores, blackheads, etc...), emerging wrinkles and a lack of radiance. Although regulation does not provide a maximum usage threshold, it is estimated that 20% is a reasonable limit for home cosmetic treatments. At very high concentrations (>20%), peels should be performed under strict medical supervision in dermatology clinics. This includes, in particular, chemical peels, which require pre- and post-treatment care. They are particularly effective for treating acne marks or pigmentation spots, as well as wrinkles. However, peels in beauty salons should not exceed 20% glycolic acid. In summary, the more concentrated the treatments are in active ingredients, the more effective they are and the deeper they act.

Beyond the concentration of glycolic acid, the pH of the solution also influences the intensity of exfoliation. The higher the pH, the more the action of the glycolic acid is neutralised.Conversely, a lower pH helps to maintain the potency of the active ingredient, thus ensuring optimal effectiveness. Similarly, the lower the pH, the more acidic the product is, and therefore more irritating.

At Typology, two products containing glycolic acid are offered for daily use:

• An exfoliating serum : Composed of 10% glycolic acid, this treatment works on the quality and texture of the epidermis by providing hydration to the skin, thanks to its stimulating effect on cellular renewal and the synthesis of hyaluronic acid, and by combating blackheads and enlarged pores. We recommend using the glycolic acid serum for 4 weeks to see its effects: resulting in a smoother and more even complexion.

• An exfoliating toner : With a glycolic acid content of 8%, this cosmetic product facilitates skin exfoliation, deep pore cleansing, and thus reduces the presence of blackheads, and tightens the pores. Consequently, the glycolic acid lotion will enable the skin to regain a rejuvenated, toned appearance, and a radiant, even complexion.

Glycolic acid is generally well-tolerated and suitable for all skin types: dry, normal, combination, and oily. However, its exfoliating action can weaken the epidermis, making it more sensitive. It's worth noting that sometimes skincare products containing glycolic acid can cause mild tingling, tightness, or redness. However, if you experience a burning sensation or intense tingling, it's possible that your skin may not tolerate it. In the face of these discomfort or irritation sensations, immediately rinse your skin and stop using the product. Don't hesitate to check the concentration of the formulas to adapt the choice of care used according to your skin's tolerance. It is, in fact, not recommended for sensitive skin and pregnant women due to its irritating effect and high concentration of active ingredients.

Furthermore, like all fruit acids, glycolic acid is a "photosensitising active", meaning it can trigger skin reactions under the effects of UV rays due to its keratolytic effect. Therefore, it is strongly recommended to apply treatments containing it only in the evening and to ensure protection from the sun during the day with a cream with SPF.

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• MAIBACH H.I. & al. Increased in vivo collagen synthesis and in vitro cell proliferative effect of glycolic acid. Dermatologic Surgery (1998).

• GARG G. & al. Chemical peeling - glycolic acid in varying concentrations and time intervals. Indian Journal of Dermatology, Venereology and Leprology (2001).

• THAPPA D. M. & co. Comparative study of trichloroacetic acid versus glycolic acid chemical peels in the treatment of melasma. Indian Journal of Dermatology, Venereology and Leprology (2010).

• HEARING V.J. & al. Applications of Hydroxy Acids: Classification, Mechanisms, and Photoactivity. Clinical Cosmetic and Investigational Dermatology (2010).

• KAWASHIMA M. & al. Glycolic acid chemical peeling enhances the resolution of inflammatory acne eruptions due to its suppressive and bactericidal impact on Propionibacterium acnes. Journal of Dermatology (2012).

• GARG V. K. & al. Comparative study of 35% glycolic acid, 20% salicylic–10% mandelic acid, and phytic acid combination peels in the treatment of active acne and post-acne pigmentation. Journal of Cutaneous and Aesthetic Surgery (2019).

• CHO N. J. & al. pH-dependent antibacterial activity of glycolic acid: implications for anti-acne formulations. Scientific Reports (2020).