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All About Alpha Hydroxy Acids

October 06, 2021



Our uppermost layers of skin are constantly undergoing cell turnover—the process of releasing dead skin cells and revealing fresh layers of skin cells beneath. Aging can cause that process to slow down, leaving skin more dull and textured—and it can even leave wrinkles more visible.

If you imagine a single wrinkle in the skin, the more dead skin cells surrounding the wrinkle, the deeper it appears! If you remove dead layers of skin, the wrinkle becomes more “shallow” and therefore less visible.

Chemical exfoliation can also help reduce the appearance of pores and "de-clog" skin! Certain acids can dive deeply into clogged pores, loosening detritus and allowing it to be cleansed away, leaving a smoother, clearer complexion.


There are two common types of exfoliation in skincare: chemical exfoliation and mechanical exfoliation.

Both have their benefits, but chemical exfoliation - when utilized properly and over a significant period of time - is often safer and less traumatic for the skin.

Mechanical exfoliation involves using a slightly rough surface (like a washcloth, a face scrub, or a cleansing brush) to slough off the top layer of skin. This process can be effective but sometimes more damaging for the skin, as it can inadvertently cause micro-cuts and inflammation. Scrubs that have crushed shells, in particular, can cut skin on a microscopic level, leaving the door open for skin infections and redness.

Chemical exfoliants - while they may sound scarier - can actually be much gentler for the skin! Alpha hydroxy acids are solutions that are slightly more acidic than the skin and can gently loosen dead skin cells, allowing you to wash dead layers of cells away when you cleanse.


Alpha hydroxy acids, otherwise known as AHAs, are acidic compounds found in nature. The most common AHAs are glycolic acid, mandelic acid, and lactic acid. All are effective exfoliators, while also promoting moisture within the skin, a fantastic combination!

Due to its large molecular size, lactic acid is one of the gentler AHAs (as it has difficulty absorbing into the deepest layers of skin), and is therefore an excellent starting place for beginners to chemical exfoliation.

Mandelic acid also has a fairly large molecular size, rendering it quite gentle, but it has the added benefit of being oil-soluble, allowing it to travel deep into pores that are clogged with sebum.

Glycolic acid is the most common AHA, and has the ability to travel the most deeply into the layers of skin due to its small molecular size. Glycolic acid, in combination with other ingredients, is also an effective treatment for melasma, a type of hyperpigmentation.

AHAs can be extremely effective at increasing cell turnover and increasing skin’s hydration. Their moisture-binding properties allow them to keep skin moisturized while simultaneously purging dead skin cells.

All AHAs help boost collagen production, leaving skin firmer and plumper, and can help reduce the appearance of fine lines and wrinkles, leaving users with a more youthful, revitalized appearance!


The term “pH” stands for “potential hydrogen,” and is measured as a method of describing the scale of a solution from acid to alkaline. Skin requires a certain level of acidity in order to kill bad bacteria that may be present. But, if skin is too acidic, it can start to become irritated and inflamed. On the other hand, if skin’s balance is too alkaline, it may become excessively dehydrated and prone to infections.

The skin’s moisture barrier, also called the “acid mantle,” protects skin from pathogens, germs, irritants, and environmental factors while simultaneously keeping moisture locked in. Since skin’s natural ideal pH is around 5.5, skincare products should be pH balanced to help skin maintain that ratio.

Alpha hydroxy acids have a pH that is just slightly more acidic than that of the skin (around 3.5-4.0), which is what allows them to gently strip away dead skin cells safely.


For skin that’s prone to overproducing oil, clogged pores can be a near constant battle. Acid exfoliants, particularly glycolic acid, can dive deeply into pores, loosening sebum plugs and allowing them to be expelled through cleansing.

AHAs can also help fight active acne, as they help increase cell turnover, kill bacteria, and promote healing. Salicylic acid, a beta hydroxy acid, can also effectively treat acne and can sometimes be used in conjunction with AHAs for that purpose.


Chemical exfoliants come in a wide range of concentrations. A good rule of thumb is to start by using products with low concentrations of acid.

For AHAs (glycolic, mandelic, and lactic acids) an 8-10% concentration (or less) is a good starting point, any higher and you might experience some irritation while your skin adjusts.

Some skincare companies sell creams with concentrations up to 15-20% acid, but those are designed for consumers who have successfully used lower concentrations for a long period of time.

Using lower acid percentages gives your skin time to adjust to a new routine, and if needed, you can always increase the percentage of acid in your products later.


You may see acid products called “peels” which often have a much higher concentration of alpha hydroxy acids (around 20-30%, or even higher!). It’s best to leave those higher concentrations alone unless under the supervision of a dermatologist, as you can unintentionally give yourself severe chemical burns.

While they may seem appealing due to promises of speedy results, you can also speedily lose a great deal of skin, and not just the upper layer you were hoping to exfoliate away. Using products with the lower concentrations of acid, however, can be completely safe for use at home when used as directed, though the results may take a bit more time to be visible.

If you do choose to use a chemical peel with a high concentration of acid, be sure to follow the directions extremely closely, and don’t leave the product on the skin longer than is recommended!


There are many AHA products on the market, and you may be wondering whether you need a toner, lotion, cream, or spray. Thankfully, all can be effective, as long as you utilize your skincare products in the correct order.

However, you only need one AHA product in your routine - using more than one may result in irritation. It’s best to include an AHA as part of your nighttime routine, as it can mildly increase your sensitivity to the sun - so be sure to apply sunscreen each morning!

  • If using an AHA cleanser, use it as your first skincare step each night.
  • If using an AHA toner or spray, apply directly after cleansing.
  • If using an AHA serum, apply directly after cleansing and/or toning.
  • If using a cream/lotion, apply after any cleansing/toning/serums and before any oil-based products.

Chemical exfoliants have a pH that is slightly lower than that of the skin, so for best results, allow skin to dry a bit before applying any other products on top.


Before starting any chemical exfoliant regimen, make sure to add sun protection to your routine. Freshly exfoliated skin is more sensitive to sun exposure. This makes sunburns  much more likely, and sun damage can be difficult to reverse!

To begin utilizing a chemical exfoliant in your routine, make sure you do a patch test first by rubbing the product onto a small area of skin (the skin on the "inside" of your elbow is a good place to test) and waiting 24 hours to see if any unexpected reactions result. If your patch test is successful, use your chemical exfoliant two to three times a week at first, allowing yourself at least a day between each use to avoid sensitivity. Don’t be surprised if you feel a bit of tingling after your first several applications, that will eventually dissipate with consistent use.

As your skin becomes more accustomed to the acid treatment, you can slowly increase your weekly usage (up to every day, if you wish). While it’s best to start your usage on the low end of acid percentages, you can eventually increase your acid concentrations if needed—but remember to do so slowly and gradually, paying careful attention to your skin’s comfort and appearance. Most people never need an AHA concentration of more than 10%.


To increase the “brightening” power of your AHA product, you may choose to look for complementary ingredients, including:

Grapefruit and lemon oils: citrus acids can be very powerful, so skincare brands often use diluted versions (don’t use any citrus fruit at home, as they can give you severe chemical burns!). Using products that include these oils, much like AHAs, can increase cell turnover and help give skin a “brightened” appearance.

Aloe vera: aloe can help reduce redness in the skin, and can also provide a slightly cooling effect - which may be helpful if you’re a first-time AHA user!

Hyaluronic acid: this water-binding ingredient can help boost the humectant properties of your AHA, leaving your skin firm and moisturized!


Purging, a temporary worsening of your skin’s condition, can sometimes occur when first using a chemical exfoliant or acid product. Because the acids penetrate deeply into the skin, they can often cause deep blemishes and impurities to come to the surface, resulting in temporary inflammation and breakouts. Keep in mind that this result is actually a move in a positive direction, as your skin is finally able to rid itself of any deep clogging! Typically, the skin’s condition improves within a few weeks, and will continue to look better and better with time.

If you’re planning for a big event, make sure you start using your chemical exfoliant at least 3-6 months ahead of time. You don’t want to be in a purging stage if you’re planning for something important. Give yourself plenty of buffer time to make sure you can get through the purging stage and start to see the benefits of your exfoliant.


No matter how tempting it may be to try at-home DIY skincare treatments, always remember that you can seriously damage your skin if you don’t do your research first! Remember - skin’s normal pH is around 5.5, which is slightly acidic, allowing it to protect itself from bacteria and pathogens.

However, solutions that are too acidic can cause serious burns; on the other hand, if skin becomes too alkaline, it can become dehydrated, causing disruption in its barrier capabilities and a dull appearance. Skincare products should always be geared toward keeping skin’s pH at optimal levels.

Keep in mind that an effective alpha hydroxy acid has a pH of around 3.5 - 4.0, which is slightly lower than that of the skin, which has a pH of 5.5.

  • Baking soda, a popular ingredient in DIYs, has a pH of around 9, which is highly alkaline and can severely dehydrate the skin.
  • White vinegar, another popular at-home skincare ingredient, has a pH of around 2.5 - 3.5, very acidic - leaving you at risk for chemical burns.
  • Pure lemon juice has a pH of 2, extremely acidic, and should never be applied directly to skin.

Remember, these ingredients are chemicals! When used improperly, even ingredients commonly found in the home can cause severe skin damage.


Alpha hydroxy acids have a near-miraculous ability to loosen dead skin cells, clean out pores, and reverse signs of aging. AHAs have been shown to:

  • Reduce wrinkles
  • Fade hyperpigmentation
  • Reduce pore size
  • Treat acne/blemishes
  • Improve skin’s moisture barrier
  • Promote collagen production

AHAs are a skincare powerhouse, and when utilized properly, they can leave your skin looking younger, clearer, and brighter!