AHAs and BHAs - A Beginner's Guide (Part 1)

A Beginner's Guide to AHAs and BHAs (Part 1) :: Crappy Candle

It's been 5 months since I kicked off The Acne Experiment; last month I started testing out more traditional products. I'll be doing review on two Paula's Choice salicylic acid exfoliators in the next few weeks (the review is here), but before I get to that, I thought it would be prudent to talk a little about why I opted to try these kinds of products, and what they can do for the skin.

I chose to try formulated products because I know acne can be caused by a hell of a lot of things. Sometimes acne is caused by products you are using, other times it is caused by products you aren't using, and sometimes it's caused by something entirely unrelated (like diet, hormones, genetics, or environment). I'd be willing to wager that more often than not, it's a combination of all three of these issues. I know that for me at least, there are even zones of my face that respond to certain things better than others.

As such, simply replacing existing cleaners, moisturizers, and treatments with natural alternatives may not be enough to cure acne. Often times, more potent active ingredients are needed to make skin clear.

Enter, chemical exfoliants.

AHAs (Alpha Hydroxy Acids) and BHAs (Beta Hydroxy Acids) are the two classes of chemical exfoliants. Chemical exfoliants work in a similar way to physical exfoliants (like a Clarisonic, microdermabrasion, or a face scrub) in that they remove the built-up dead skin cells to reveal new, smoother skin. Both chemical and physical exfoliation can be beneficial for acne because those dead skin cells are a component to acne formation -- when combined with sebum, they can clog pores. Exfoliation is also beneficial for anti-aging, scarring, and hyper-pigmentation, as well as other non-acne skin conditions such as keratosis pilaris or melasma. Chemical is often recommended over physical because, when applied with the proper technique and dosage, chemical tends to be gentler on the skin.

Here's how AHAs and BHAs differ:

Main Qualities of Chemical Exfoliants

AHA - Alpha Hydroxy Acid BHA - Beta Hydroxy Acid
AHAs exfoliate the surface of the skin BHAs exfoliate the surface of the skin and inside pores
AHAs are water soluble BHAs are fat/oil soluble
AHAs tend to moisturize skin BHAs tend to dry out skin
AHAs have humectant qualities BHAs have antibacterial qualities
AHAs have been shown to build collagen BHAs have been shown to reduce inflammation

BHAs are most frequently recommended for acne because it can get down into pores, while AHAs tend to be recommended for anti-aging benefits and skin texture improvements. This is not to say that AHAs are not beneficial to acne-prone skin or that BHAs are only for acne-prone skin, however. The combination of the other, non-exfoliant ingredients may determine what works best for your skin. Additionally, some AHAs are less moisturizing, and others have antibacterial qualities. There are a few fantastic AHAs, so if you're looking for something for acne, you shouldn't limit yourself to browsing one kind.

The following are the 7 chemical exfoliants you're most likely in anti-acne and anti-aging skin care products:
  • Salicylic Acid - Salicylic is the one and only BHA for skin. In skincare circles, the terms are often used interchangeably. Salicylic Acid is most effective as an all over exfoliator in 1% to 2% concentration, but can also be used at a higher % as a spot treatment. Salicylic Acid is a relative of Aspirin (be careful with those allergies, guys).  AKAs: 2-hydroxybenzoic acid, benzoic acid
  • Glycolic Acid - Glycolic Acid is the biggie when it comes to AHAs. Most major brands that make an AHA product will use Glycolic in their formulations. It is most effective in the 8% to 10% concentrations, but as your skin adapts, you may be able to handle more potent stuff. Glycolic Acid is distinct from other AHAs because it has the smallest, simplest molecular structure. This means it is a good choice for potent acne fightin', but it is also the most likely to irritate.  AKAs: hydroxyacetic acid, hydroxyethanoic acid 
  • Lactic Acid - Lactic Acid is another popular choice of Alpha Hydroxy Acids. In my experience, I have found Lactic Acid to be very moisturizing. This is because it is a humectant (ie it attracts water). Lactic Acid is fantastic for dry skin. It is most effective in 5% to 10% concentrations.  AKAs: milk acid, hydroxypropanoic acid
    • Recommended Brands: St. Ives* (5%), if you're looking for body exfoliation, AmLactin lotion (12%) is amazing
      *2/18/15 - St. Ives Exfoliating pads have been been discontinued :( The best replacements I can find that are ONLY lactic acid are from Silk Naturals and GOW. I'll be offering more info on this when I do a proper St. Ives review in a few weeks. (the review is DONE and HERE; So is my Silk Naturals review, it's HERE)
  • Mandelic Acid - This is a "new kid on the block" amongst AHAs. Mandelic Acid has a molecular structure that is larger than both Lactic and Glycolic Acids, making it a gentler choice for sensitive or reactive skin; because it's so new, very little has been written about it. What we do know is that it is moderately humectant (moisturizing) and it has anti-microbial properties. Mandelic Acid is made from bitter almonds. (What the what is a bitter almond?)  AKAs: amygdalic acid, almond acid, benzeneacetic acid 
  • Malic Acid - Malic acid comes from apples and unripe fruit, and is part of the reason why Raw Unflitered Apple Cider Vinegar is such a good choice for natural skincare. Malic Acid is one of the larger AHA molecules, so it's quite gentle (and frequently combined with other AHA formulations).  AKAs: Apple Acid, Fruit Acid (this is ambiguous though since citric, glycolic, and tartaric are all technically "fruit acids")
    • Recommended Brand: Bragg or Trader Joes - It's also great in hair, but it stinks while drying.
  • Citric Acid - Derived from citrus fruits, citric acid is an AHA, but is usually used in conjunction with other ingredients in good skin care products. Citric acid is used primarily as a means to adjust the pH of an AHA chemical exfoliant to their most effective level.  AKA: aciletten
  • Tartaric Acid - Tartaric acid is derived from grapes and found in wine. It is often used to adjust pH of different cosmetics & products, but can also be used as an exfoliant in the same way other fruit acids are used. Like citric acid, tartaric is a larger molecule, making it ideal to use in conjunction with other exfoliants to "pave the way" for smaller AHAs to get in there and do their thing. (source)  AKAs: threaric acid, uvic acid
A note on Paula's Choice: Paula's Choice is a very useful resource even if you don't use their products. They sell a full line of skincare/cosmetics, but they have a ton of useful articles and something called the "Beautypedia" where they analyze the ingredients and effectiveness of cosmetics from a ton of brands. This is especially exciting if you're like me and enjoy scrutinizing product labels in the middle of the isle at Target. (Almost) Everything I know about exfoliants, I learned from Paula.


This is Part 1 of my 3 part series on chemical exfoliants:

Part 1:  A Beginner's Guide to AHAs & BHAs
Part 2:  10 Things to Know Before Using an AHA or BHA
Part 3:  Do Natural AHA and BHA Alternatives Work?

ALL Acne Experiment Posts are listed at The Acne Experiment MOTHER HUB.

A Beginner's Guide to AHAs and BHAs (Part 1) :: Crappy Candle
A Beginner's Guide to AHAs and BHAs :: Crappy Candle


  1. I'm not sure if my comment posted so I will repost.
    Nucelle mandelic acid 10% cleared up my skin after trying everything like you have.
    I also forgot to mention eating eggs helped a lot because of vitamin A. I wish I could eat liver but I can't stomach it. There is a definite connection between the thyroid and hormonal acne. Beautyeditor has a great article on the connection between vitamin A and acne that proved invaluable.

  2. Nice write up! Nucelle mandelic acid 10% cleared up my skin after trying everything like you have.
    I also forgot to mention eating eggs helped a lot because of vitamin A. I wish I could eat liver but I can't stomach it. There is a definite connection between the thyroid and hormonal acne.


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