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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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
Thanks for the summary. It is also a reminder to wear a sunscreen after applying the alphabet soup.
I think this needed to be explained for a lot of people. Great article.
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.
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.
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.
Yes, we posted on aspirin masks before.
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
I was wondering, how is BHA made? I mean, where does it come from? Is it a naturally occuring substance or is it born in a chemical lab? :/ I’d really love to know.
Hi,
I’ve thought a lot about this, and while it intuitively makes sense – oil soluble = prevent acne better, I don’t think it necessarily works that way (& it hasn’t been my personal experience). The AHA’s do after all peel, whether the skin is oily or not. How “deeply” they peel is about the concentration and how long you leave it on – there’s only so much of the surface you’ll want peeled.
As for getting into the (blocked / collapsed) hair follicles and diluting the oil there, maybe salicylic acid does that, but so does alcohol or any organic solvent no?
I can see how diluting the sebum deeper in the hair follicles and also being antibacterial in there maybe does prevent some acne – but I don’t see how just because it dissolves in it it removes any of the sebum. Maybe it makes it easier to remove with soap/cleanser, I don’t know? It’s still not water soluble, or closer to the surface, is it?
Anyway, the specific benefit we get from the acids is the peeling, dissolving “glue” between the top layers of skin cells (and not just dead skin cells – dead skin cells you can just brush or scrub off, a chemical peel always involves injuring the skin slightly which is why it regenerates faster in response, and I think that repeated injury is what in the long run leads to more collagen production and wrinkle prevention).
That’s how they can prevent acne – preventing hair follicles from being blocked by dead and collapsed skin cells – and I don’t think AHA’s and BHA’s work differently here.
Another thing about salicylic acid is it’s always in isopropyl alcohol or something similar since it’s not water soluble, and I don’t like drying my skin even more when I’m peeling it.
As the majority of people only purchase skin care/acne treatment products when they need to get rid of something unwanted and not to prevent acne or skin damage, then it is better to stick with the products that contain Beta hydroxy acids as they will help you get rid of your acne quicker