What are hydroxy acids (HA), and why are people adding them to their skincare routine? I’ve heard people talk about these exfoliants all over social media which have been used to treat skin conditions like acne and keratosis pilaris. Because of my inquisitive nature, I took it upon myself to discover what they are, how they work, and why exactly they’re beneficial, and wrote all my interesting findings in this article so you don’t have to! I’ll also be explaining the chemistry behind HA’s and focusing on glycolic (AHA) and salicylic acid (BHA).
Let’s talk science
A hydroxy acid is a chemical compound with one or more hydroxyl (R-OH) groups attached to a carbonyl group. This just means that the structure of the molecule contains one or more oxygens bonded to a hydrogen and a carbon sharing a double bond with another oxygen atom.
The difference between an alpha α and a beta β HA is the position of that OH group. If it’s directly bonded to the carbon of the carbonyl group then it’s an alpha hydroxy acid AHA, and if it’s directly attached to an alpha carbon, then it’s a beta hydroxy acid BHA. By now you might be thinking… How does the structure of the acids matter? The truth is that its structure heavily affects the way they interact with your skin.
In the cosmetic world, HA’s are defined as chemical exfoliants that gently rid your skin of accumulated dead skin cells. Glycolic and salicylic acid do exactly this, but since their chemical structures aren’t the same, they perform differently.
How do AHA’s & BHA’s work?
Glycolic acid, an AHA, has a small chemical structure and is water soluble, meaning that it dissolves in water. For these reasons, it targets the skin’s surface as well as penetrates the skin deeper than salicylic acid, which is a larger molecule due to its benzene ring. Because of this, it targets hyperpigmentation by exfoliating the old skin cells piled up in those areas. Also, since it’s water soluble, people with drier skin are better off using this AHA.
On the other hand, salicylic acid, a BHA, is oil soluble (lipophilic), so it works by breaking down the oil in your skin and eventually dissolving it. Because of this and its larger structure, it penetrates the skin superficially. However, this doesn’t mean it isn’t as effective as glycolic acid. Since it’s oil soluble, it not only targets the skin’s surface like glycolic acid but also targets the pores, oftentimes packed with excess oil. Therefore, this HA would suit best for someone with oily skin or with acne. All in all, both HA’s will have an end result of an improvement of skin texture by smoothing out the skin.
But wait… Should I really put acid on my face?
The word “acid” might come across as off-putting and overall alarming. I mean… Are we really putting acid on our faces now? The truth is that, at low concentrations, hydroxy acids are relatively safe to use. I say “relatively” because it all depends on how sensitive your skin is. Still skeptical? Well… What if I told you each lemon contains about 8% of citric acid? That’s the molecule that makes it sour! This fruit contains a type of acid, and yet they’re still safe to consume (in moderate amounts). Notably, over the counter skin care products containing HA products contain a lower concentration of HA’s. Of course, there are some products that have higher percentages, but these are medically prescribed and controlled. Also, only very high concentrations of these acids are used in laboratories for experimentation.
“Which one is better for me?”
As previously mentioned, it all depends on your skin type. If your skin is prone to be dry, then glycolic acid is a better choice due to its water solubility, meanwhile an oily skin type would benefit much more from salicylic acid. However, always talk to a medical doctor or dermatologist before you ever try to change your skincare routine.