Mandelic Acid, an active ingredient to soothe acne?

Is gentler than glycolic acid.

Is just as effective as glycolic acid or salicylic acid in treating acne.

It possesses anti-bacterial and anti-inflammatory properties, in addition to its exfoliating action.

Suitable for sensitive skin, when used alone.

Can be combined with salicylic acid to enhance its effects in the fight against acne.

Acne is an inflammatory disease of the pilosebaceous follicle. It is caused by multiple overlapping factors:

• Androgens (dihydrotestosterone), male hormones secreted by the testicles in male subjects and by the adrenal glands and ovaries in female subjects, stimulate the sebaceous glands to produce more sebum, which is responsible for facial seborrhea;

• The epidermis does not exfoliate as well as it should, leading to a build-up of dead cells on the skin's surface that can block the pores. Indeed, this follicular hyperkeratosis forms a keratinous plug that hinders the normal flow of sebum;

• A specific type of bacteria that lives in the pores, Cutibacterium acnes formerly known as Propionibacterium acnes, feeds on sebum. However, when it is present in excess, it creates an oxygen-free environment conducive to their growth and proliferation;

• The increase in the number of bacteria triggers an inflammation that the body detects and responds to by sending white blood cells to eliminate them. More specifically, these bacteria secrete enzymes into the hair follicle and sebaceous gland to hydrolyse the sebum's triglycerides into irritating and pro-inflammatory free fatty acids, which are responsible for the formation of red spots (papules).

Once the white blood cells have killed the bacteria, they die and leave behind pus, which is literally made up of decomposing white blood cells. Your body eventually absorbs this pus and the healing process begins.

There exist various types of acne which can be classified as either inflammatory or non-inflammatory.

• Non-inflammatory/retentional acne includes whiteheads and blackheads which form as a result of pore blockage. If the "plug" is exposed to air, it oxidises and takes on a brown/black colour (blackhead), but if it is not exposed to air and is deep, it appears as a flesh-coloured bump (whitehead).

• Inflammatory acne encompasses papules (red bumps), the pustules (red spots with a white head), the nodules (larger and deeper bumps that can be red or purple) and the cysts (larger and deeper red bumps filled with pus).

Themandelic acid is an alpha-hydroxy acid (AHA), which is naturally found in bitter almonds. It acts as an exfoliant by breaking down the chemical bonds that hold together the dead skin cells so they can be removed from the skin's surface. It has a high molecular weight (MW = 152.14 g/mol), meaning it penetrates the skin more slowly than other AHAs such as glycolic acid (MW = 76.05 g/mol) and lactic acid (MW = 90.08 g/mol).

Themandelic acid can be beneficial for your skin in several ways, including:

• Treatment of existing acne and prevention of new acne;

• Skin Exfoliation;

• Stimulation of collagen production to improve the appearance of wrinkles and fine lines;

• Skin Hydration;

• Diminishing the appearance of brown spots;

• Inhibition of bacterial proliferation;

• Reduction of inflammation.

Given its mild nature, the mandelic acid sometimes needs to be combined with other AHAs (glycolic acid, lactic acid, tartaric acid...) or BHA (salicylic acid) to enhance its effectiveness. However, on its own, it serves as an excellent option for sensitive skin.

Mandelic acid has been extensively studied for its ability to eliminate skin blemishes and treat skin conditions such as acne. Indeed, it presents an excellent option for acne-prone skin, as it addresses the four main causes of acne. It "controls" sebum secretion, prevents bacterial growth, avoids pore blockage by enhancing the skin's natural exfoliation process, and reduces inflammation. Moreover, compared to other AHAs and BHAs, it is less likely to cause skin irritation or post-inflammatory hyperpigmentation.

Anti-inflammatory, antibacterial, exfoliating... mandelic acid combines all the properties needed to tackle spots. A 2020 study even showed that a peel using mandelic acid (45%) is just as effective as a peel usingsalicylic acid (30%) for treating mild to moderate facial acne, while causing fewer irritations and side effects. Indeed, in Indian acne patients, the use of 45% mandelic acid peels once every two weeks for 12 weeks led to a significant resolution of comedones, papules and pustules.

Another study also suggests the effectiveness of 10% mandelic acid peels (+ 20% salicylic acid) in reducing both non-inflammatory and inflammatory lesions, when applied every two weeks for three months. Furthermore, they are also beneficial in nodular and cystic acne, and acne scarring. Additional research suggests that 5% mandelic acid is equally as effective in improving acne papules and pustules as 10% mandelic acid over an 8-week period. Thus, there is no need for a high concentration to achieve results.

How does mandelic acid work to improve acne? The mechanism of action remains unknown, but it could be due to alterations in keratinisation, and the anti-inflammatory and antibacterial activity of mandelic acid could also play a role in improving acne. Furthermore, with all these benefits, mandelic acid could particularly contribute to the prevention of spots.

• TAYLOR M. B. Summary of mandelic acid for the improvement of skin conditions. Cosmetic Dermatology (1999).

• SARKAR R. & al. Glycolic acid peels versus salicylic-mandelic acid peels in active acne vulgaris and post-acne scarring and hyperpigmentation: a comparative study. Journal of the American Society for Dermatologic Surgery (2008).

• SAHU P. & al. Comparative study of the effectiveness and safety of 45% mandelic acid versus 30% salicylic acid peels in mild-to-moderate acne vulgaris. Journal of Cosmetic Dermatology(2019).

• SWIERGIEL A. H. & co. Antimicrobial properties of mandelic acid, gallic acid and their derivatives. Mini-Reviews in Medicinal Chemistry (2021).