Alpha Hydroxy Acid and the Skin

Alpha Hydroxy Acids

Alpha-hydroxy acids (AHA’s) are naturally occurring acids, derived from the sugars in particular plants. Glycolic acid is derived from sugar cane, Lactic acid from milk and Malic acid from apples. Mandelic acid, a relatively new innovation in skincare, is found in bitter almonds. These acids work at the very base of the outermost layer of the epidermis (stratum corneum).

This layer is made of dead, flat skin cells that shed about every 2 weeks. By dissolving the cement that holds these dead skin cells together, AHA’s increase cell turnover and influence the structure of new stratum corneum being made. This results in skin that is more flexible, smoother, and more even in tone. AHA’s are also weak hydroscopic agents, meaning that they absorb moisture from the atmosphere and hydrate the skin.

cross section of the skin
cross section of the human skin

A balanced AHA skincare regimes will:

  • reduce fine lines
  • refine skin texture
  • firm skin
  • fade hyperpigmentation

The result is skin that looks fresher, radiant and more luminous. AHA products are beneficial for aging, sun-damaged and blemished skin.  AHA products can only remove superficial lines, wrinkles and blemishes and cannot act as a cure for the effects of middle/advanced age or deep scars.

There is a lot of misleading information published about alpha hydroxy acids. Here are a few of the common myths concerning AHA’s :

Myth 1

Alpha hydroxy acids thin the skin: This myth is based upon a misunderstanding as AHA’s actually increase the skin thickness. However, AHA’s do reduce the layer of dead skin cells on the surface (the stratum corneum). This is why AHA’s have a

beneficial effect on photo-damaged skin, which suffers from a thickening of this dead skin cell layer. At a deeper level, however, the long term use of AHA’s promotes collagen production and encourages plumper skin. [BC Kwak, et al, J Inv Dermatol 108 (4) 572 Abstract 207 (1997), CM Ditre et al, J Am Acad Dermatol 35 287-295 (1996), WP Smith, J Am Acad Dermatol 35 388-391 (1996)]

Myth 2

Alpha hydroxy acids cause sun sensitivity. Used correctly, alpha hydroxy acids do not increase sun sensitivity. Sun sensitivity occurs when skin is irritated and inflammation occurs. Those with very fair colouring are especially susceptible to this since their skin tends to be more sensitive. Avoiding high concentrations (15% or more) or products with pH’s lower than 2.5 can help avoid this. Of course, a sunscreen should always be worn whether you are using alpha hydroxy acids or not. Although AHA will not cause sun sensitivity, exfoliating layers of dead skin that have built up may allow more UV to pentrate.

Myth 3

Use of Salicylic Acid or a mechanical scrub will produce identical exfoliation benefits. Salicylic acid works from the uppermost layer of the skin, dissolving skin layer by layer. Mechanical scrubs work only to remove already loosened skin cells on the upper layer of skin. Alpha hydroxy acids work at the lowermost levels of the stratum corneum. This activity encourages a smoother, flatter cell layout in the stratum corneum, something that other exfoliating agents cannot achieve.

Myth 4

Anti-Wrinkle benefits of AHA’s are due to their exfoliating nature. While it is true that the exfoliating nature of AHA’s contribute to softer skin that is more even in tone, the clinical effects of AHA’s in modifying wrinkles and photo-aging are due to increased skin thickness and new collagen formation.