AHA and BHA acids for the skin: What's the difference?

AHA and BHA Acids


AHA otherwise known as Alpha-hydroxy-acid - a type of acid that is derived from sugarcane, milk or fruit.

As chemical exfoliators, AHA's work by peeling away the dead skin cells on the skins surface, revealing fresh new skin cells underneath.

AHA's exfoliate the skin by attacking the glue that holds the skin cells together. By doing this it makes for an even resurfacing of new skin. 


Here are types of AHA's:

Glycolic Acid - The most common AHA, derived from sugarcane. It's the strongest becuase of its small molecular size, which makes it the most irritating.

Lactic Acid - The seconf most common AHA, derived from milk.  It's a gentler alternative to glycolic acid. Good for sensitive skin types.

Mandelic Acid - A mild AHA derived from bitter almonds. Usually its combined with other acids.

Malic Acid - A mild AHA derived from apples. It wont do enough on its own so its usually combined with stronger AHA's.

Tartaric Acid - An AHA coming from grapes. It's oftern used to stabalize other acids pH levels.

Citric Acid - An AHA derived from citrus fruits. It is similar to tartaric acid in that it regulates pH. It also is used as a perservative.

BHA - A chemical exfoliator that soften and dissolve keratin, a protein that forms part of this skin structure. This helps to loosen dead skin cells, so they're easily sloughed off.


BHA's also work inside the pores, where they not only dissolve keratin plugs, but also help to regulated keratinizatin ( cell turnover and shedding). For example a condition like acne is associated with hyperkaratinization-meaning the body is shedding skin cells too fast. BHA's slow down this process, so the cells function longer before they flake off (meaning they're less likely to clog pores).

The main exfoliants you'll see in skincare products are:

Salicyclic Acid: The most common BHA. However, it is not as irritating as glycolic acid (the strongest AHA) because it has a large molecular size, as well as anti-inflammatory properties.

Betaine Salicylate: A BHA derived from sugar beets. It is a gentler alternative to salicylic acid, and according to a study by the manufacturer, is equally effective. 4% betaine is said to be equivalent to 2% salicylic acid.

Salix alba or Willow bark extract: A natural BHA extracted from plants. Although the salicin content converts into salicylic acid, it is much weaker ( so it wont give you comparable results for exfoliating or treating acne).


AHA and BHA similarities:

exfoliating and smoothing, brightening, fades hyperpigmentation, firming skin and reducing wrinkles, hydrating, clearing and preventing mild acne.


AHA and BHA differences:

Solubility: AHA's are water soluble so they dissolve in water while BHA's are oil soluble so they dissolve in oils which makes them able to push through sebum and sebaceous follicles.

Area of Action: AHA's work on the top layers of skin, but BHA's work on the skin surface AND inside the pores. 

Concentration: AHA's need to be used in concentrations of at least eight percent in order to be effective, whereas BHA's only need a concentration of around 2% Nowdays BHA's can be found in doses asl ow as 0.5%).

Decreasing oil production: AHA's dont have an effect on sebum. BHA's can reduce excess oil by slowing down sebum production.

Clearing and preventing acne, blackheads and clogged pores: While both acids can help with mild acne by sloughing off dead skin cells. BHA's also work on a deeper level to clear trapped sebum in the pores and prevent new clogs from forming. They also slow down oil secretion and loosen blackheads, making them easier to extract.

Shrinking pores: Technically, you cant change the size of your pores - but they can look bigger when they are filled wirh debris, which makes them stretch out. While AHA's dont affect pores, BHA's can help them look smaller by keeping them clean.

Irritation: Any acid can be drying and irritating if you use it as the wrong concentration or pH, or of you apply it too frequently for your skin. However AHA's are more often associated with irritation, redness and inflammation. BHA's tend to be less irritating, thanks to thier larger molecular size. The alkso have anti-inflammatory prpoerties.

Photosensitivity: AHA's increase your skin's sensitivity to the sun, making it more vulnerable to sun damage and premature aging. While sunscreen is essential always, BHA's actually have some photoprotective effects.

Skin wounding: AHA's are skin wounding agents because they encouarge cells to self-destruct through apoptosis ( cell death). BHA's are non-wounding agents, as they simply loosen the bonds between skin cells ( a more physiological process). 

AHA, BHA or both?

Now that you know the difference between AHA's and BHA's, what oes that mean for your skin concerns?


If you have acne:

BHA's are the way to go. Salicylic acid is proven to reduce the number and severity of acne lesions, and is superior to benzoyl peroxide. Look for a concentration of 2% salicylic acid or its equivalent, 4% betaine Salicylate. Keep in mind that you may experience initial purging. Which is a good thing !

If you have oily skin:

Only BHA's will reduce oil production. It may take some experimenting to find the best dose for your skin - between 0.5 to 2% salicyclic acid, or one to 4% betaine salicylate.


If you have dry or sensitive skin:

Lactic acid is the best AHA for these concerns, asit's one of the gentlest and most hydrating acids. Look for a concentration between 5-8% to start, oving up as high as 10% if tolerated. However mild BHA would be an equally suitable option, such as 0.5 percent salicylic acid or 1-2% betaine salicylate.

If you have pigmentation:

Both AHA's and BHA's will help, but I think BHA's are your best bet - especially if you have darker skin. Unlike AHA's they wont trigger post-inflammatory hyperpigmentation, which is a risk for many ethnicities, BHA's also have some photoprotective properties, so youre less likely to create new pigment. Go for a higher concentration if you can, such as 2% salicylic acid or 4% betaine salicylate. For best results, use it in conjunction with niacinamide.


If you have wrinkles:

Glycolic acid, lactic acid and salicylic acid have all been shown to produce changes in dermal thickness and the depth and number of fine lines and wrinkles. for best results, you'll want around 8% or more glycolic or lactic acid, 1% or 2% salicylic acid. Again, just keep in mind that AHA's can make your skin more inflamed and vulnerble to sun damage, which can exacerbate signs of aging.


If you want to combine acids:

And what about AHA's and BHA's together? Is there any benefit to both? 

use a combo AHA - BHA treatment with a mild blend of acids

Apply your AHA and BHA at different times of day. I suggest using your BHA in the morning and your AHA at night or apply them on alternate nights

apply your BHA on your oilier areas like the T zone and your AHA everywhere else. That way, you're applying both at the same time, but not doubling up on acid.

Layer one acid on top of the other, but this increases your risk of irritation and dryness ! Since AHA's and BHA's are close in pH ( betweem 3.0 and 4.0), you wouldn't need to wait in between just to apply the product with the thinnest texture and/or lowest pH first.



No matter which acid you choose, the key is finding one that's the right strength for your skin, and not overdoing it. I believe you'll get better results from using a milder acid on a regualr basis as often as daily. 


For more questions or concerns on products containing AHA and BHA acid, please call our office at 949 679 8679




Cosmetic Laser Center of Irvine

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