Annie’s asking: I’ve noticed that a lot of skincare products have one or the other of these acids in them, and I’m not sure what they’re used for. What’s the difference between alpha hydroxy acid and beta hydroxy acid?
The Left Brain’s alphabet soup:
AHAs and BHAs, as they’re affectionately known, belong to a class of chemicals known as organic acids. They’re both characterized by a carboxylic acid group and a hydroxyl or OH group. The difference between the two is the location of the OH group: in Alphahydroxy acids the OH group is on the first carbon next to the acid group, in Beta hydroxyacids it’s on the second carbon. Common examples of AHAs include lactic, glycolic, and citric acids. The primary BHA used in cosmetics is salicylic acid.
What do AHA’s do?
AHAs are water soluble and act on the upper layers of skin. They help break down the “cement” that holds cells together so they are good at peeling off old, dead cells and speeding up the production of fresh skin. You can find them in anti-aging products like Neoteric’s AHA Souffle and Alpha Glycolic Face Cream. AHAs can be dangerous if over used because they make your skin more sensitive to sun exposure. (Here’s a good reference that gives more details.)
What do BHA’s do?
BHAs are more soluble in oils than in water. That’s why salicylic acid is used in acne products: it can penetrate oil-filled pores and break down the dead skin cells that clog pores and cause inflammation that leads to pimples. If you want to learn more, read our post on the causes of acne. Sal Acid can be found in products like Neutrogena Salicylic Acid Acne Treatment and Nature’s Gate Organic Body Wash.
The Beauty Brains bottom line:
Beta hydroxy acids are better for battling acne on oily skin. Alpha hydroxy acids are for good for refreshing damaged skin.
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Leah Says:
Thanks for this! Have often wondered what the differences were cosmetically, however i did know that they were named according to the position of their hydroxyl group!
You can thank my chemistry teacher for that! x
Beckie Temple Says:
Thanks for the summary. It is also a reminder to wear a sunscreen after applying the alphabet soup.
Sandy Says:
I think this needed to be explained for a lot of people. Great article.
Gloria Says:
Yay! I read about this from Nadine Haobsch (sp?) book Beauty Confidential not too long ago.
I then proceeded to purchase Paula’s Choice 2% BHA Gel. I’m thinking about getting the AHA lotion for my mom since she has sun spots and what not.
Trubey Says:
If the BHAs are salicylic acid, can I crush aspirin tablets to make my own inexpensive versions of more expensive products?
Perhaps this sounded like a flip comment, but I am seriously considering it.
thebeautybrains Says:
Trubey: Crushing aspirin doesn’t work because its made of acetylsalicylic acid, not salicylic acid. The two are not the same. Search our blog for “aspirin” to read more.
thebeautybrains Says:
Yes, we posted on aspirin masks before.
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The Derma Divas Says:
There are always great posts here that are very educational and informative.
To read more about the differences between AHA’s and BHA’s as well as Retinol, etc., check out:
http://myfacialfacts.com/index.php/2008/07/07/wont-exfoliation-dry-out-my-skin/
To your skin’s health!
The Derma Divas