What’s an AHA?

If you’ve ever used any type of professional exfoliating product, chances are it contained an Alpha Hydroxy Acid (AHA). So, what are these acids and how do they benefit the skin?

AHA’s are naturally occurring acids that range from low to high exfoliating potential. Technically speaking, if you’re an organic chemistry nerd, they contain a hydroxy group on the first carbon chain (beta hydroxy acids contain a hydroxy group on the second chain). They assist in exfoliation by freeing the sebum that helps  our skin cells literally stick together. Exposure to AHA’s allow them to lift off freely and reveal newer skin cells that give us a brighter appearance. This can help to unclog skin, lighten areas of hyperpigmentation, and brighten dull skin. The most common of these include (ordered from strongest to most gentle):

  •  Glycolic Acid: Derived from sugar cane. It is the smallest in molecular size of the AHA’s and therefore can penetrate the deepest. It’s widely used in the skin industry and has particularly helpful effects for brightening the skin and correcting signs of aging. While it can be drying because of its strength and astringent-degreasing potential, glycolic acid is hydrophilic (water-loving), therefore it helps retain moisture after use. Best to use on oilier, less sensitive skin types.
  • Lactic Acid: Derived from milk. Another very common AHA that can be used for slightly more sensitive skin types. It will benefit those with uneven tone, premature signs of aging, and correct dryness because of its hydrophilic nature. Lactic acid can even be used on individuals with rosacea. Though, always consult with your skin care provider or dermatologist.
  • Mandelic Acid: Derived from almonds. A very gentle AHA that is beneficial at reducing hyperpigmentation and correcting acne. It packs a punch when combined with lactic acid. This acid can also be used on sensitive, rosacea prone skin. Personally, this is one of my favorites because it is the least irritating and consistently gives beautiful results for a broad range of imperfections.

All of these acids have a fairly low pH, therefore have an astringent and exfoliating effect on the skin after immediate use. Our skin has a natural pH that ranges from 4.5-5.5 called the acid mantle. AHA’s have even been shown to increase the efficacy of our skin’s barrier function when we use the appropriate pH (stick with an AHA cleanser close to your skin’s natural pH level. Cleansers that are closer to neutral or basic may have temporary beneficial effects but they weaken the barrier over time).

Products can range from cleansers, toners, brightening treatment solutions, moisturizers, and chemical peels. Peels will have the most dramatic effect due to the higher percentage and concentration of the AHA and the lower pH.

When using any kind of mild topical AHA at home like a toner or moisturizer, know that you want to avoid direct sun exposure directly after application. While the half-life (the time it takes for the ingredient to become half its original strength) of AHA’s are pretty short, ranging from 30 minutes to 3 hours, it still strips the outer most layer of skin from the surface. This outer most layer is what protects us from UV damage, therefore if you’re planning on being outside while AHA’s are in your skincare regimen it’s better to just use them at night, wait at the very least 12 hours post AHA use, and always wear a physical blocker (zinc oxide or titanium dioxide) sunscreen.


Reasons to avoid AHA’s:

  • You were recently waxed
  • Have an active sunburn
  • Are pregnant or nursing
  • Are using prescription tretinoin (this can vary- for low percentage retinols, it can be fine to use)
  • Have extremely sensitive skin or severe rosacea
  • Are planning on being in the sun


I’d like to know, what are your favorite alpha hydroxy acids? Comment below if you have more questions!

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