Topical application: what are the benefits of mandelic acid?

Is an alpha-hydroxy acid (AHA).

Can exfoliate the skin.

Has antibacterial, anti-inflammatory and antioxidant properties.

Mandelic acid (INCI name: Mandelic Acid), also known as amygdalic acid, is a type of alpha-hydroxy acid (AHA) alongside glycolic acid, lactic acid, citric acid, malic acid and tartaric acid. This organic acid, whether naturally derived or synthetically produced, originates from bitter almonds, although it can be found in many other plants.

It notably aids in providing a more targeted exfoliation. Indeed, it performs a non-mechanical and less abrasive keratolytic action that eliminates dead cells clogging the pores. Its large molecular size (MW = 152.14 g/mol) allows it to remain on the skin's surface and exfoliate superficially: each type of AHA has its advantages layer by layer due to their molecular size. It thus improves the skin's condition without causing any side effects.

When dead skin cells, dirt, and bacteria accumulate on the skin's surface, it results in an uneven and undesirable texture to the touch. The gentle exfoliation enabled by mandelic acid is essential for enhancing the skin's appearance and texture.

promotes controlled desquamation for a "new skin" effect. Thanks to this "peeling-like" action, it thus accelerates the natural process of cell renewal (re-epithelialisation), which is the arrival of new cells on the surface. Compared with glycolic acid and lactic acid, the peeling result with mandelic acid is less profound.

Furthermore, mandelic acid helps the skin to stay hydrated for longer. Indeed, by improving the quality of the skin barrier, formed of newly renewed keratinocytes, it allows to limit the evaporation of water contained within the skin. It also promotes a better absorption of active ingredients contained in the subsequent skincare products.

Escherichia coli, Staphylococcus aureus and Candida albicans are normal flora of the human body. However, an increased number of these bacteria can cause infections in certain cases such as acne. Yet, the antibacterial nature of mandelic acid makes it highly effective in reducing existing acne and preventing future skin outbreaks.

Its advantage over other agents is also its anti-inflammatory effect, thus causing less erythema and hyperpigmentation than other AHAs might. Add to this its ability to penetrate the skin slowly and gently, and the way it effectively exfoliates the skin's surface without overly drying it out, you get the perfect acid for acne-prone skin.

The stratum corneum, the uppermost layer of the epidermis, is composed of 10 to 20 layers of dead cells (corneocytes). These are continuously removed and replaced by new cells rising from the lower layers: this is the process of desquamation. A complete cycle of cellular renewal lasts on average 28 days.

However, this natural process of elimination slows down with age and can take up to 45 days to complete in older individuals. Indeed, the accumulation of dead cells on the skin's surface gives a dull and grey appearance. The less smooth surface of the skin reflects light less effectively.

The use of mandelic acid is the quintessential step for dull and tired skin. It helps to shed excess dead cells to make way for new skin cells for a brighter and more even complexion. Similarly, the build-up of corneocytes can clog pores; their removal thus helps to combat the formation of imperfections (enlarged pores, blackheads, spots).

Since mandelic acid does not trigger an inflammatory response in the skin, unlike other acids such as glycolic acid, it is particularly effective in reducing the pigmentation of brown spots. Age spots, post-acne hyperpigmentation and melasma, mandelic acid can indeed fade the appearance of pigmented spots of all types. By refining the horny layer, the melanin pigment content of the basal layer decreases and disperses more evenly, which improves hyperpigmentation and evens out the complexion.

More specifically, mandelic acid, with its exfoliating properties, will remove dead cells enriched with melanin from the skin's surface. Each dissolved layer thus helps to diminish the appearance of pigmented marks until they "completely" disappear. Moreover, due to its large molecular weight, mandelic acid tends to linger on the skin's surface for longer, slowly penetrating the superficial layers of the epidermis, thereby producing a uniform epidermal effect. Research conducted in 1999 even demonstrated that mandelic acid can improve hyperpigmentation of melasma by 50% in approximately 4 weeks with a lotion containing 10% mandelic acid.

Mandelic acid can also be used on mature skin. Indeed, it can help to reduce the effects of the ageing process, particularly in diminishing the appearance of wrinkles and restoring the elasticity of your epidermis. During the exfoliation process, mandelic acid promotes the removal of damaged and aged skin cells in a controlled manner to replace them with younger and firmer cells by activating skin renewal, thus reducing the appearance of wrinkles.

Further research suggests that chemical exfoliants such as mandelic acid stimulate dermal fibroblasts to promote the synthesis of new collagen, elastin and glycosaminoglycans (hyaluronic acid), which are building blocks of the skin, in the papillary dermis through an indirect, yet unknown mechanism.

Another study has shown that mandelic acid stimulates or balances sebum production and thus helps to maintain skin hydration when it is dry or damaged. Finally, a study conducted to evaluate the effectiveness of a topical treatment based on mandelic acid revealed that after four weeks of use, it managed to tighten the skin by 23% and toincrease the skin's elasticity on the lower eyelids by 25%. The authors of the study thus concluded that mandelic acid is an effective option for improving skin quality.

One of the benefits of mandelic acid is its ability to reduce pore size. But how does it do this? Studies explain this outcome by the property of mandelic acid to inhibit the formation of comedones, thus leading to a decrease in follicular openings. Since mandelic acid exfoliates and unclogs pores, a "secondary" effect of this action is the reduction of pore size.

Mandelic acid also possesses a potential antioxidantcapacity. Indeed, studies have shown that it can be used to minimise oxidative stress caused by reactive oxygen species, by donating an electron to the free radical and thus reducing their level in cells. Consequently, mandelic acid could be an interesting bio-active agent to prevent and inhibit the damage that cells and biologically important substances such as DNA and proteins undergo due to the action of free radicals, which can lead to a number of complications such as premature skin ageing.

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