Bible of Acids: Understanding AHAs and BHAs

AHAs, BHAs, exfoliants, hydrators! Acids can be difficult to understand much less know how to incorporate into a routine. What are they? How should they be used? Does it matter what skin type you have?

What’s a girl (or guy) to do?

Fortunately we have done all of the work for you. We like to call this, our Bible of Acids. All you could ever want to know about the most common (and some less common) acids used in modern cosmetics. Due to the breadth of information available on acids this will be a series discussing the many different types of acids with the first installation focusing on AHAs and BHAs. Let's dive right in!



Each person’s skin is different. If you have never used acids then you do not know how your skin might react.

1. Start slowly: Patch test and/or do a wash that contains the acid ingredient to see how your skin reacts

2. Not just for your face: Acids can be used on more than just your face (chest, décolletage, back, shoulders, etc)

3. Patience is a virtue: Results from acid use take time and regular application

4. There’s an App for that: There is an app called RYNKL that will help you track subtle changes and tell you if the products are working for you

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alpha-hydroxy acids

Generally, you can think of these as nature’s chemical exfoliators.

Alpha-hydroxy acids are low molecular weight (read:small) naturally occurring acids, derived from the sugars in specific plants. Their small size allow them to penetrate deep into the very base of the outer layer of skin (the stratum corneum), dissolving the bonds that hold dead skin cells together. This increases cell turnover and influences the structure of new cells of the outer skin layer. Resulting in skin that is more flexible, smooth, and even in tone. As if that were not enough, they are also humectants or they attract water in the environment to your skin.

Several studies, including those done by the FDA, indicate that applying AHAs to the skin results in increased UV sensitivity. However, this sensitivity is reversible and does not last long after ending the use of AHAs. Therefore, if you are using products, particularly cream-based, with AHAs don’t forget the sunscreen. Even if you are only applying your AHA’s at night, still use sunblock during the day. The sensitivity doesn’t end when you wake up!

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Acetic Acid

Acetic acid is essentially vinegar and too acidic to use directly on your skin/hair. If you dilute the vinegar with water or aloe vera juice you can use it as a hair rinse. Rinsing your hair with apple cider vinegar will help with hard water, seal and condition the cuticles, and leave your hair with a natural shine. If you dilute with rose water you can create a refreshing yet exfoliating facial toner. You can also drink a tablespoon a day to help treat skin problems form the inside out. 

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Citric Acid

As you may have already guessed citric acid is derived from citrus fruits (e.g. lemons, oranges, etc.). Like acetic acid, citric acid is too caustic for direct use but in the right concentration it be a great exfoliator. It is often used as a pH adjuster in skin care products. It is a powerful antioxidant that fights free radicals, rebuilds collagen, and encourages the growth of new cells.

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Glycolic Acid

Glycolic acid is derived from sugar can plants. It has the smallest molecules of all the AHAs, so it can easily and deeply penetrate the skin. It encourages cell turnover which brightens your complexion. Dead skin cells absorb light but new healthy cells reflect light which gives your complexion the appearance of being brighter or radiant. Glycolic acid also rebuild collagen and elastin (i.e. reduce fine lines and wrinkles) and lightens dark spots. It is a less caustic more effective alternative to acetic or citric acids. Two of our favorite glycolic acid treatments are PIXI Glow Tonic and Drunk Elephant T.L.C. Framboos Glycolic Night Serum.


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Lactic Acid

Lactic acid can be derived from milk, fruit, and vegetables but most forms used in cosmetics are synthetic because it is easier to formulate with and stabilize. lactic acid has all the benefits of glycolic acid but in a gentler less-irritating formula. It is also the most hydrating of the AHAs. Therefore, this is a good introductory acid for people with dry and or sensitive skin types. One of our favorite lactic acid treatments is Sunday Riley Good Genes.


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Malic Acid

Malic acid is one of the lesser known AHAs. It can be derived from apples but the cells of your body make it naturally every day. It improves hyperpigmentation by decreasing the production of melanin. It promotes shedding of the outer layer of skin cells, exfoliates buildup and pore clogging impurities, improving the skin's texture and reducing the appearance of fine lines and wrinkles. One natural brand that uses malic acid is Elemis. Try their Pro-Collagen Oxygenating Night Cream and let us know what you think.

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Mandelic Acid

Mandelic acid is derived from bitter almonds. It has all the benefits of traditional AHAs but in a gentler formulation. However,  it is less effective than glycolic acid due to its larger size (2x the size of glycolic acid) and slower penetration into the skin. It can increase sebum production! So not great for oily skin types. Unlike other AHAs it is oil soluble (ie. dissolves in oil) allowing it to work within the pore and on the surface of the skin. Therefore, it is great for treating acne and hyperpigmentation. This acid would also be a good introductory acid for those with sensitive skin.



beta-hydroxy acids

Beta-hydroxy acids or BHAs are similar to AHAs, but, there are a few important differences. BHA’s are oil soluble, so they work on the skin’s surface and inside the pore. They are ideal for normal to oily acne-prone skin with enlarged pores. They can kills acne causing bacteria. BHAs can also calm irritated/inflamed skin, even skin tone, and hydrate/smoothen the skin’s texture. BHA's are gentler exfoliants than their AHA counterparts. They are also good for treating keratosis pilaris. Check out our post here to learn more about keratosis pilaris.

The lone-wolf in this category is Salicylic acid. It is the only BHA commonly used in modern skincare products. Salicylic acid is derived from the bark of the Wlillow Tree. It has been used for medicinal purposes since about 500 b.c. but rather as a pain reliever and fever reducer than a skin treatment. Native Americans also used willow bark to treat pain, fever, and inflammation. Now it is used to treat many skin conditions, including: acne, dandruff, psoriasis, seborrheic dermatitis of the skin and scalp, calluses, corns, common warts, and plantar warts, depending on the dosage form and strength of the preparation. You can get salicylic acid treatments in prescription strength formulations as well as over the counter. A concentration of 1-2% is good for treating acne and unclogging pores but you will need a higher concentration if you want to use it as an exfoliant.

*Disclaimer: One important thing to know about salicylic acid is that it is very similar to the active ingredient in aspirin, acetylsalicylic acid. As such, anyone allergic to asprin should avoid using anything with salicylic acid as it can cause a similar allergic reaction. Better safe than sorry!

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Other Key Players.....

In addition to the AHAs and BHAs there are other "acids" that do wonders for the overall health and appearence of your skin. These acids work well alone but are best used in conjunction with AHAs and/or BHAs. Continue to follow us to learn more about antioxidants and the anti-aging acids.







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