Mandelic Acid and Hair: What are the Benefits?

Derived from bitter almonds, mandelic acid is an aromatic alpha-hydroxy acid (AHA), primarily used in skincare to enhance the texture and appearance of the skin, as well as to treat acne, hyperpigmentation and the effects of ageing, notably due to its keratolytic, keratoplastic and anti-microbial properties. To reap its benefits, one should opt for skincare products containing at least 5 to 10% mandelic acid. In excess, it can lead to side effects.

Unlike other fruit acids, mandelic acid is generally safe and well-tolerated by all skin types. Its large molecular size allows it to penetrate the epidermis slowly, making it a better alternative to glycolic or lactic acid for sensitive skin. However, in some cases, it can cause side effects, such as dry skin, a warm sensation, tingling, redness, and itching.

Shampoo, scalp exfoliation... mandelic acid can also be incorporated into the formulation of hair care products. Its gentle exfoliating power can help to remove the build-up of scales adhering to the scalp, as well as excess sebum and all other underlying impurities, thereby freeing the pores. This encourages cell renewal, that is, the emergence of new cells, and sanitises the scalp, while reducing inflammation.

A recent study has investigated the use of a shampoo containing ichthyol (1.2%), mandelic acid (1.2%), zanthalene (< 1%) and honeydew honey (< 1%) in the treatment of mild to moderate scalp psoriasis. Thirty subjects with mild to moderate psoriasis, aged between 18 and 65, were instructed to apply the shampoo three times a week for 12 weeks. They were also instructed not to use any other shampoo or topical medication on the scalp, as this could potentially compromise the effectiveness of the treatment.

Shampoo Composition : Ichthyol has anti-microbial and anti-inflammatory activity. Themandelic acid has exfoliating effects and stimulates cellular renewal, well-known properties that help to eliminate dandruff. Zanthalene is an ingredient extracted from Sichuan pepper, a Chinese spice used to soothe discomforts by acting on neuromuscular communication within the skin's structure. Honeydew honey has moisturising, softening and soothing virtues; it helps to maintain a soft and protected scalp, and alleviates irritations.

As a reminder, psoriasis is a recurring chronic inflammatory skin disease characterised by an abnormal hyperproliferation of keratinocytes, leading to a thickening of the stratum corneum, vasodilation, increased permeability, and inflammation. Scalp involvement is a common clinical aspect of psoriasis. It is characterised by erythema (redness) and desquamation (scaling), sometimes associated with a sensation of itching. Despite a wide range of therapeutic options, scalp psoriasis remains difficult to treat.

The results obtained demonstrate a significant reduction in the severity of scalp psoriasis. Indeed, the use of the shampoo significantly reduced erythema in 87.50% of patients and scaling in 89.05% of patients. Furthermore, no side effects were observed or reported. The researchers conclude by suggesting that this shampoo could serve as an effective adjunct treatment to modulate scaling, itching, and inflammation, the hallmarks of scalp psoriasis.

• CAMELI N. & al. Clinical and videodermoscopic assessment of the effectiveness, safety, and tolerability of a shampoo containing ichthyol, zanthalene, mandelic acid, and honey in the treatment of scalp psoriasis. Skin Appendage Disorders (2018).