What are the effects of glycolic acid on acne?

Acne is an inflammatory disorder of the skin, more specifically of the hair follicles, characterised by the emergence of superficial acne lesions ( comedones, papules and pustules ) or deep ones (nodules and cysts ). This condition is very common among teenagers, but also occurs in some adults. It primarily affects areas rich in sebaceous glands, such as the face, upper back, chest, neck, shoulders, etc...

Acne is the result of several interlinked factors. It all begins with either an excessive production of sebum, or a thickening of the wall of the sebaceous gland duct (which connects the follicle to the skin surface), thereby narrowing its diameter and partially blocking the diffusion of sebum out of the sebaceous gland. In other cases, acne can be induced following a hyperkeratinisation (poor evacuation of dead cells), thus trapping the sebum in the follicle. This seborrheic retention is responsible for the formation of comedones (blackheads and whiteheads).

Indeed, this fat-rich environment can lead to the abnormal proliferation of a pathogen, Cutibacterium acnes (formerly listed under the name Propionibacterium acnes), on the skin surface and in the hair and sebaceous follicles. This abnormal multiplication of the bacterium Cutibacterium acnes, usually well tolerated by the skin, triggers the secretion of pro-inflammatory factors. The resulting inflammation can also be due to damage caused by the follicle. At this stage, papules or nodules may form. However, the follicle can subsequently be superinfected by other microorganisms present on the skin. This can then lead to the appearance of a pustule or a cyst containing pus.

Acne is linked to multiple origins:

• The hormonal fluctuations (during puberty, a few days before menstruation, during pregnancy, at the time of menopause);

• The genetics (family history);

• Certain medications (oral contraceptive treatment, cortisone derivatives, certain antibiotics, lithium, certain antidepressants, antiepileptics, immunosuppressants);

• Theuse of comedogenic cosmetics ;

• The stress (production and release of Substance P by nerve cells, which can influence sebum production);

• The repeated friction on a specific area of the skin.

Once healed, acne can leave temporary or permanent scars (brown spots), especially when the acne has been particularly severe.

Glycolic acid serves as a companion for oily skin and acne-prone skin. Its main property is to be keratolytic , thus preventing the accumulation of cellular waste on the surface of the epidermis. Indeed, through simple contact and without rubbing, glycolic acid weakens the lipid bonds between the cells of the horny layer, thereby freeing the skin from its layer of dead cells. This property gradually eliminates pore obstruction and promotes the evacuation of sebum.

It is also equipped with a sebum-regulating action. Indeed, glycolic acid helps to combat the abnormal accumulation of sebum in the dilated pores of the skin, which is the cause of acne lesion formation. Known as being the smallest of the alpha-hydroxy acids (A.H.A.), glycolic acid manages to easily penetrate the layers of the skin. It thus acts on the surface but also in depth.

Studies have reported that glycolic acid also exhibits a bactericidal activity of interest in an acidic pH environment around 3 to 4.5, even at low concentrations (< 10%). It thus helps to inhibit the proliferation of the Cutibacterium acnes bacteria on the skin of patients suffering from vulgar acne, particularly by disrupting the integrity of the bacterial cell membrane. Generally, high concentrations of glycolic acid (> 30%) are used to exfoliate the skin and unclog pores, while lower concentrations (< 15%) are used to prevent pore occlusion.

Finally, glycolic acid allows to brighten and even out the complexion of the face. It then appears to reduce acne scars, as well as pigmentation spots. This phenomenon is linked to its role in eliminating skin cells filled with melanin on the surface of the epidermis and in regenerating cells at the basal layer of the skin, but also to its ability to inhibit the overproduction of melanin, thus preventing the pigments that cause spots from marking the skin.

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

• TSANKOV N. & al. Drug-induced acne. Clinics in Dermatology (2017).

• 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).