Skin Acids: A Friend or Foe?

Alpha Hydroxy acids (AHAs) have become increasingly popular in anti-ageing creams, brightening creams and peeling solutions. These magical acids work by weakening the cellular glue that holds dead skin cells together, thereby acting as an exfoliant to remove old acne marks, sun-damaged skin and uneven skin tone.

The AHA family of acids include glycolic acid, citric acid, lactic acid, hydroxycarprylic acid and malic acid. These are naturally derived from sugar cane, sour milk and fruits. 

They can also be used at much higher concentrations in peeling solutions to treat acne, scars, melasma, deep hyperpigmentation, roughness, age spots, and seborrhea. Due to the intensity of these peeling solutions, they should always be performed under dermatologist supervision.

Glycolic Acid - A Friend or Foe?

Sugar cane is more than a tantalising refreshment! They are also a source of Glycolic Acid, a common ingredient used in dermatologic and cosmetic formulations. Glycolic Acid has a long proven track record and is widely researched. Studies have shown Glycolic Acid reduces skin wrinkles by increasing the synthesis of glycosaminoglycans and skin thickening.

Glycosaminoglycans are proteins that attract and bind water to the skin to provide hydration. Glycosaminoglycans can hold nearly 1,000 times their weight! They are also essential for keeping collagen and elastin in good condition. Glycosaminoglycans are also used by the body as lubrication for joints and for supporting connective tissues such as cartilage and tendon. We are not suggesting applying Glycolic Acid to the skin is going to have any effect on your joints, but you can see how important this protein is!

The effectiveness of Glycolic Acid depends on its concentration, pH of the formulation and also time exposure. Glycolic Acid is most effective at a lower pH and higher concentration. When the pH falls below 3 however, this can cause issues such as irritation and inflammation. When introducing Glycolic Acid into your skincare routine for the first time, always start with a lower concentration. Choosing a glycolic acid cream formulation over a gel formulation can also help reduce irritation. The presence of alcohol in gel formulations leaves more free acids on the skin, thus likely to cause irritation.

Glycolic acid can penetrate the deepest and fastest and thus; is the most effective amongst its AHA peers. Due to its fast-acting nature, glycolic acid can be more irritating compared to other hydroxy acids. The irritation can be reduced with strategic formulation and also by slowly introducing Alpha Hydroxy Acids into your skincare routine.  

The popularity of Glycolic Acid has grown over recent years, and some may argue there is a love-hate relationship for Glycolic Acid among beauty enthusiasts due to its photosensitivity profile. When used correctly (e.g. applying sunscreen when outdoors), Glycolic Acid can induce skin rejuvenation, stimulate new skin cell production and reduce or even delay the onset of fine lines. It is also naturally occurring and is plant derived. Whether Glycolic Acid is a friend or foe will largely depend on the individuals' experience and priorities.

Lactic Acids

Similar to glycolic acid, lactic acid exfoliates the upper layers of the skin, thereby reducing dryness and flakiness. Lactic acid is a larger molecular molecule when compared to glycolic acid, making their actions more gentle and better tolerated by those with sensitive skin.  

Citric Acid

Citric Acid is a much weaker acid and is used widely across many industries. In skincare, it is commonly used to reduce the pH of formulations. 

In foods, it can function as a preservative, pH regulator, stabiliser, and boost flavour profiles with its characteristic sharp, sour taste. In pharmaceuticals, Citric Acid can act as an anticoagulant and chelating agent to prevent clots. 

Malic Acid

Malic Acid is derived from fruits. In skincare, Malic Acid is used as a mild exfoliant, usually in concentrations of 1-2% in toner solutions. It can also be used in lower concentrations to adjust the pH of formulations and also to boost the effects of other AHAs such as Glycolic Acid and Lactic Acid. 

Malic Acid can also be used as a flavour enhancer owing to its sour characteristics.

When is the best time to use Alpha Hydroxy Acids?

AHA products can be used morning or night. The use of sunscreen during the day is vital to protect new skin cells and prevent photosensitivity. 

Author: Helen Huynh (B. Pharm) MPS

References: 

1. Babilas, P et al. (2012). "Cosmetic and Dermatologic Use of Alpha Hydroxy Acids." Journal of the German Society of Dermatology. March, 2012. v10:488–491
2. Tang, S et al (2018). "The Dual Effects of Alpha Hydroxy Acids on the Skin." Journal of Molecules. First published: April 2018, v23(4): 863. 
3. Sharad, J (2013). "Glycolic Acid Peel: A Current Review." Journal of Clinical, Cosmetic and Investigational Dermatology. Available online: DOI:10.2147/CCID.S34029