All About Acid Exfoliation

Here is the link to the complete Infographic!→ Click here for AHA and BHA Infographic

Additional information about AHAs and BHAs is provided in the post below.

(This was a very time consuming process, and a lot of work went into creating the infographic. So if you share the infographic or any of the images below, I would truly appreciate if you gave credit and linked people back to this post. Thanks!).

**IMPORTANT DISCLAIMER: I want to provide a disclaimer because one thing that made me really nervous about sharing this post is that although I am a trained research scientist, my expertise is NOT in dermatology, cosmetic science, etc. This just started as a “cheat sheet” for myself and my friends/family and now it has morphed into something bigger. I tried to only use primary sources (like peer-reviewed scientific journals) and other scientific textbooks, but I also used some skincare reference books. I include my sources below and I will also link to a couple blogs that have written on this topic if you want to check those out as well. If you see anything you think may be inaccurate, please let me know!**

What do Acids do?

Alpha and beta hydroxy acids are naturally occurring acid extracts from plants that act as mild exfoliants. Hydroxy acids dissolve the chemical bonds between skin cells on the surface, breaking them apart and encouraging exfoliation and revealing the underlying skin. It is sometimes referred to as chemical exfoliation because it uses chemistry to exfoliate rather than a physical exfoliation where you manually abrade or scrub them away.

This helps reveal a more radiant appearance and decreases look of fine lines and improve skin tone and texture.  

The human skin is in the process of constantly being renewed. This usually takes about 10-15 to up to 30 days for our skin to turnover (this is the “skin cycle”) if you allow the old dead skin to stay on top of the skin, this gives you a dull appearance. The cell cycle begins to decrease at about age 25 (which is so sad!). If you exfoliate this you get a more radiant appearance and a decreased in the fine lines we have in our skin.

Acids not only slough away rough, dead skin and encourage the growth of new skin cells but they are also said to boost collagen production within the skin (although, this is done through a process that is not fully understood). Boosting collagen helps to make the skin stronger and more pliable, and to pull apart small wrinkles and even out skin tones.

Also, it is suspected that AHAs stimulate production of hyaluronic acid, which plumps the skin and, as a result, reduces fine lines. Lactic acid appears to have a higher capability of activating hyaluronic acid deposition (which, in turn, increased hydration). Mandelic acid also can hydrate the skin.

Why do I use Acid Exfoliants?

I used to be a BIG fan of physical exfoliators (like the ever-popular Apricot Scrub). However, two things tended to happen: First, I scrubbed WAY too hard and used them way too often. The end result was that I did some major damage to my skin. Because physical exfoliants use rough, abrasive texture, they can cause tiny tears in the skin.

I eventually made the switch to acid exfoliants to exfoliate and remove dead skin cells and to also help unclog pores and I couldn’t be happier.

Through the use of acid exfoliants, I personally have noticed the following

  • skin appears smoother (by improving the texture of skin) and I have a more even-toned complexion
  • reduction in clogged pores and breakouts (especially with BHA’s)
  • reduction in post-breakout acne scars
  • fine lines appear less noticeable
  • dryness and flakiness is reduced
  • my serums and moisturizers seem to work more effectively (most likely because the acids “clear the way” for additional ingredients to penetrate skin and work their magic because the dead/dry cells on skin’s surface are removed).

This post will hopefully help to break down the different types of acids, what their strengths are, and how to evaluate them.

**Note: Just like physical exfoliants can cause damage to the skin with overuse, so can acid exfoliants. As much as I love the effects of acids, I have to remind myself constantly NOT to overuse them!**

What Are the Various Kinds of Exfoliating Acids?

These are just some of the most common acids – there are a few others not included (such as citric acid, which is often used as a pH adjuster)

There are two main kinds to consider: alpha-hydroxy acids (AHA) and beta-hydroxy acid (BHAs).

  • Glycolic and lactic are the most scientifically researched for performance validation

AHA versus BHA_1

It was brought to my attention that there is little empirical evidence to show that Salicylic acid is more effective on blackheads/pores than Glycolic acid. That claim appears to be based on the fact that BHAs are lipid/fat soluble, so they are better able to penetrate the underlying layers of skin. However, there hasn’t been any head-to-head comparisons (at least that I could find) that demonstrate a significant difference in Salicylic acid’s ability to unclog pores. That being said, I personally have found that a 2% BHA solution has done a better job at clearing out my pores than a 10% Glycolic acid solution. 

Why pH Matters

When shopping for alpha and beta hydroxy acids, you need to consider two factors:

  1. the percentage of active ingredients
  2. the acidity level (pH) of the whole product.

The way to measure how effective an acid will be is to measure its pH. Acid product is only as potent as the free acid concentration and the pH will regulate the amount of free acid. When the pH=pKa the solution contains 50% active free acid and the other 50% is neutralized—transformed into a salt that is inactive. For example, if a product says it has 10% Glycolic acid, and the pH equals its pKa then it really has 5% effective Glycolic acid that is active

Takeaway: Concentration does not have as much effect on acid strength as pH does

AHA BHA pkA

Tips

  • If the pH is above the recommended ranges, it won’t exfoliate very well. If it too far below the recommended ranges it can be overly irritating.
  • Two different products reporting the same percentage concentration (e.g., 10% glycolic acid) will not be equally effective if they have very different pH levels—but both can be advertised as an AHA product with a concentration of 10%. So being able to test your own acids with pH meters or strips can be helpful. You can also search online as the pH for different products is often reported by bloggers or by the company.
  • There is some newer evidence showing that salicylic acid is effective above 4.0, but until that evidence grows, it may be best to stick to a pH less than 4.0.

AHAs and BHAs free acid

AHA and BHA slide 3

I will follow up this post with a post that provides more information about free acid concentration as well as a list of various AHA/BHAs and their pH values. 

References

Bergfeld, W. F., Fiume, M. Z., & Andersen, F. A. (1999). Safety assessment of alpha hydroxy acid ingredients used in cosmetic products. Cleveland (OH): Cleveland Clinic Foundation.

Deprez, P. (2016). Textbook of chemical peels: superficial, medium, and deep peels in cosmetic practice. CRC Press.

D’Angelo, J. M. (2012). Milady Standard Esthetics: Advanced.

Green, B. A., Ruey, J. Y., & Van Scott, E. J. (2009). Clinical and cosmeceutical uses of hydroxyacids. Clinics in dermatology27(5), 495-501.

Kaidbey, K., Sutherland, B., Bennett, P., Wamer, W. G., Barton, C., Dennis, D., & Kornhauser, A. (2003). Topical glycolic acid enhances photodamage by ultraviolet light. Photodermatology, photoimmunology & photomedicine, 19(1), 21-27.

Lee, C. M. (2016). Fifty years of research and development of cosmeceuticals: a contemporary review. Journal of Cosmetic Dermatology.

Moy, R. L., Luftman, D., & Kakita, L. S. (Eds.). (2002). Glycolic acid peels. New York: NY: Marcel Dekker.

Paye, M., Barel, A. O., & Maibach, H. I. (Eds.). (2005). Handbook of Cosmetic Science and Technology Second Edition. CRC Press.

Saint‐Léger, D., Lévêque, J. L., & Verschoore, M. (2007). The use of hydroxy acids on the skin: characteristics of C8‐lipohydroxy acid. Journal of cosmetic dermatology6(1), 59-65.

Thueson, D. O., Chan, E. K., Oechsli, L. M., & Hahn, G. S. (1998). The Roles of pH and Concentration in Lactic Acid‐induced Stimulation of Epidermal Turnover. Dermatologic surgery24(6), 641-645.

Tung, R., & Rubin, M. G. (2010). Procedures in Cosmetic Dermatology Series: Chemical Peels. Elsevier Health Sciences.

Here are some great blog posts on this topic that you may find useful: 

http://www.labmuffin.com

  • LabMuffin created a free acid calculator for exfoliants at specific pH levels–SUPER helpful resource!

http://www.crappycandle.com

https://theacidqueenblog.com

https://fiftyshadesofsnail.com/

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9 thoughts on “All About Acid Exfoliation

    • Thank you so much! It definitely took up a ton of my time because I became a little obsessed with learning and synthesizing as much as I could. I am So very happy to hear that you found it helpful. ❤️

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  1. Im new to your blog. Love love love this post. Have an obsession with skincare (like most here!!) and acids are my current favourite. Thank you for taking the time to explain all of this so well x

    Liked by 1 person

  2. Hi Vanessa! I am so glad I found you on IG. Your post are very informative. I am new to skincare and am learning still. How often do you use acid exfoliants? Thank you so much for any feeback.

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    • I use a BHA every other morning and an AHA (or AHA/BHA blend) 3 to 4 nights a week. But if you are starting out, I would start out with 2 times a week, spaced out. Some people can have a reaction to specific types of acids (like some people can’t use a glycolic acid because it is too strong for them), so take it slow and try to get samples to check for immediate signs of irritation. 😊

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