In the history of cosmetics, no other ingredient or family of ingredients has had the impact or efficacy of Hydroxy Acids. Alpha Hydroxy Acids (AHAs) and Beta Hydroxy Acids (BHA) are a family of naturally occurring mild acids. Most AHAs and BHA are present in fruits and vegetables.
AHAs and BHA have a very large number of applications in skin care and can help many conditions, including oily and acne-prone skin, sun damage, dryness and hyperpigmentation. There are several AHAs used in skin-care treatment and that include lactic acid, tartaric acid, malic acid and by far the best known AHA, glycolic acid. Salicylic acid and citric acid are also often included when discussing hydroxy acids, but they are actually Beta Hydroxy Acids.
Research shows that AHAs and BHA can also improve skin thickness and cell turnover, increase collagen content, reduce discolorations, and improve pore function by reducing the number of clogged pores.
AHA vs BHA
The chemical difference between Alpha and Beta Hydroxy Acids is the location of the Hydroxy Group on the carbon chain of the acid. Alpha indicates that the group is on the first carbon atom, whereas Beta means that the group is on the second carbon atom.
AHAs are best for those with normal to dry and/or sensitive skin, and BHA is best for those with normal to oily or breakout-prone skin. This is because AHAs cannot penetrate oil and, therefore, cannot get into the pore lining. BHA can penetrate oil and, therefore, can get into the pore where it can improve and repair pore function while dissolving blockages of dead skin cells and oil that contribute to blackheads and acne. Whichever you choose, always monitor your skin’s response, and remember, irritation is never the goal.
The Right Concentration > pH Level > Ingredients = The Right Product
The goal with chemical exfoliants is to use one effective AHA (between 5% and 10% concentration) or one BHA (1% to 2% concentration) product, and only as needed – which may be twice a day, once a day, or once every day, depending on your skin type and its response. The effective AHA and BHA products not only have formulations with the appropriate concentrations but also have a pH between 3 and 4, which is critical if those ingredients are to be effective as exfoliants. To allow exfoliation to properly occur, it is important NOT to contain fragrance or other irritating ingredients but to contain beneficial ingredients like water-binding agents, antioxidants or anti-irritants.
Alpha Hydroxy and Beta Hydroxy Acids can be used in many products, including cleansers and toners, but are most effective when used in leave-on products such as treatment gels, serums, or moisturizing creams.
If you decide to use an AHA or BHA product, you may find benefit from using a mechanical scrub once a day or once every other day but never use a scrub when you are using AHA or BHA.
The Different Exfoliants
Lactic Acid is an Alpha Hydroxy Acid occurring naturally in milk, both an exfoliant and a hydrophilic.
Tartaric Acid is an Alpha Hydroxy Acid occurring naturally in grapes and passionfruit.
Malic Acid is an Alpha Hydroxy Acid derived from apples.
Glycolic Acid is the most frequently used Alpha Hydroxy Acid, exfoliant and hydrophilic.
Citric Acid, or Beta Hydroxy Acid, is most often used as a pH adjuster, but can also be used as a mild exfoliant.
Salicylic Acid is a Beta Hydroxy Acid with exfoliating and antiseptic properties; natural sources include sweet birch, willow bark and wintergreen.