What Is An AHA (Alpha Hydroxy Acid) In Skincare?

Citric Acid AHA derived from Citrus Fruit

The term AHA is popping up everywhere in the skin care world, and if you’re wondering what exactly an AHA is you’ve come to the right place. While it does literally sound like a eureka moment ‘AHA!’ it’s actually an abbreviation of Alpha Hydroxy Acid; although the results AHAs offer are definitely worth shouting about. It is good practise to know exactly what is going into your skincare products so you can best tailor them to your individual needs.

What is an AHA (Alpha Hydroxy Acid) In Skincare?

AHAs or Alpha Hydroxy Acids area group of weak organic acids that can be both naturally occuring or synthetic. These acids are used in skincare formulations for their excellent exfoliating properties. The use of an AHA is a form of chemical exfoliation which works to slough off the outermost layer of dead skin cells, revealing a brighter, more even complexion underneath.

The key benefits of topical application of AHAs are as follows:

  1. Excellent exfoliating properties: The acidic nature of AHAs make them an excellent exfoliant. These acids work to remove dead skin cells and break up debris in the pores to reveal clearer, smoother skin with continued use.
  2. Can help minimise and prevent acne/breakouts: By exfoliating deep into the pores AHAs can help clear clogged pores and prevent them from occuring in the first place. Acne forms when a pore becomes clogged with dead skin cells, oils and other contaminants.
  3. Clear away blackheads: Certain AHAs work deep into the pores to promote skin cell turnover as well as softening and breaking up the matter that causes blackheads. Continued use of AHA’s can prevent blackhead formation.
  4. Can even skin-tone: By promoting skin cell turnover AHAs can help even skin tone, whether this be from sun damage, scarring or even age spots.
  5. Promote collagen production: Some AHAs (namely Glycolic Acid) promote collagen synthesis. Collagen is a protein responsible for the skin’s structure, firmness and elasticity.
  6. Anti-aging, minimise fine lines and wrinkles: By boosting the production of collagen and promoting skin cell turnover, AHAs can help to minimise fine lines and wrinkles associated with aging.
  7. Improve product absorption: By exfoliating the skin properly, absorption of skincare products is improved. Prior to exfoliating the skin is covered with dead skin cells and other contaminants. Removal of this outer layer of skin through physical or chemical means will lead to easier product absorption.

AHA can refer to any one of the acids in the group of AHAs.

What are the different types of AHA (Alpha Hydroxy Acid)?

There are many AHAs available on the market. They come in many forms, serum, moisturiser, peels, all in different concentrations. Below are some of the most well known AHAs:

Glycolic Acid

Potentially the most well known Alpha Hydroxy Acid. Glycolic is a naturally occuring compound found in sugar cane, although the form in skincare products is typically synthetic [2].

Glycolic acid is a well researched acid, many medical studies have proven it’s excellent exfoliating and skin rejuvenating properties. Okano Y et al. [3] found that glycolic acid accelerates collagen synthesis and regulates degradation. Usuki A. et al. [4] found that glycolic acid increases the turnover of the epidermis while also inhibiting melanin production in melanocytes. This can be an important function in cancer prevention from UV-related damage.

Glycolic acid is more effective at clearing out pores and sebum regulation than other AHAs. This is because glycolic acid has the smallest molecular size, meaning it can penetrate deep into the skin to deliver results. Glycolic acid is also safe for use across all skin types and ages.

The Ordinary Glycolic Acid AHA 7% Toning Solution

If you’re new to Glycolic acid try this 7% toning solution by The Ordinary. Regular use of this toner will help clear the skin and provide an ongoing glow.

Lactic Acid

Lactic acid is found in sour milk products, although like Glycolic Acid it is typically synthesised in a lab for stability. Lactic acid can adjust acidity in skincare products and it also possesses disinfectant and keratolytic properties [5].

Lactic acid is a slightly milder acid with a larger molecular size. This means it cannot penetrate as deep into the skin as glycolic acid, but it is still excellent at exfoliating the outer layer of dead skin cells.

The main benefits of lactic acid include; stimulating collagen production; improve skin hydration; brighter, more even complexion, increased skin cell turnover. Lactic acid is the preferred acid for those with sensitive skin as it is milder than other AHAs.

AHA Lactic Acid 10% + HA 2% by The Ordinary

This high strength 10% Lactic Acid peeling formulation by The Ordinary is excellent for exfoliating the skin and also reducing skin inflammation.

Malic Acid

Malic acid is found in apples, although the synthetic form is used in skincare formulations (you might have noticed this is a common theme).

Malic acid has the largest molecular size of the three acids already mentioned, but this does not take away from it’s excellent skin renewing properties. Malic acid can help to boost skin cell turnover, minimise signs of aging, restore pH balance and brighten the skin.

Malic acid also comes with the additional benefit of anti-oxidant effects, meaning it can help to fight skin damaging free-radicals.

Citric Acid

As the name suggest Citric acid is found in many citrus fruits. Like Malic acid, Citric acid also an exfoliant that comes with anti-oxidant properties. These anti-oxidants are excellent for the skin as they protect the skin and neutralize harmful free radicals.

Citric acid is commonly used as an acidulant in skincare formulations, meaning it’s used to regulate the pH in skincare products[6].

Citric acid is typically more harsh than the other AHAs due to it’s low pH. Definitely something to be aware of if you have sensitive skin or skin conditions such as rosacea and eczema.

Tartaric Acid

Tartaric acid is found in grape wine but the synthetic form is added to skincare formulations.

Tartaric acid is usually added together with either glycolic acid or salicylic acid (BHA) where it helps boost the effectiveness of the product. This can either be through regulating the pH of the product, or by effectively creating ‘layers’ of acids that work on different areas on the skin.

For example, tartaric acid has a large molecular size and so would best suit exfoliation on a surface level, whereas glycolic acid can penetrate pores and work deep into the skin to promote cell turnover. This becomes especially important in regulating the strength of skincare formulations, many different acids can be used at lower concentrations instead of one acid at a high concentration. This reduces the possibility for skin irritation, redness and inflammation.

References

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6017965/

[2] https://en.wikipedia.org/wiki/Glycolic_acid

[3] https://pubmed.ncbi.nlm.nih.gov/14756525/

[4] https://pubmed.ncbi.nlm.nih.gov/14756523/

[5] https://en.wikipedia.org/wiki/Lactic_acid#Pharmaceutical_and_cosmetic_applications

[6] https://en.wikipedia.org/wiki/Citric_acid#Cosmetics,_pharmaceuticals,_dietary_supplements,_and_foods