If you’re starting to get serious about your skincare routine, you’ve probably seen the abbreviations “AHA” and “BHA” come up regularly. What are these two ingredients, what do they do, and which one is best for your skin type?
Alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) are both exfoliants. If you’ve read “Learning to Take Great Care of Your Skin,” you already know that exfoliating is an important step in your skin care routine. That’s because sloughing off dead skin cells helps to stimulate cell turnover, improves the appearance of your complexion, and gives your other products a better shot at being effective.
Manual vs. Chemical Exfoliants
Exfoliants fall into two different categories. There are manual exfoliants, which are characterized by a gritty texture, and usually include sugar, ground apricot shells, or microbeads. Manual exfoliants work by literally scrubbing off dead skin cells.
This might feel like you’re getting your skin squeaky clean. However, manual exfoliants are abrasive by nature and easy to overuse, which can damage your skin by creating micro tears.
Both AHA and BHA are considered chemical exfoliants. They work to exfoliate the skin and stimulate collagen, making your complexion appear brighter, smoother, and healthier. However, unlike manual exfoliants, they do so by way of a chemical reaction.
While either AHA or BHA can be part of your regular skin care routine, they have inherent qualities that make each a more desirable option for different skin types and troubles. Here’s a breakdown of what each does best:
Alpha-Hydroxy Acids (AHA)
Once skin cells reach the outer layer of your epidermis, the stratum corneum, they become flattened, keratin-filled envelopes that are no longer capable dividing.
These envelopes are called keratinocytes, and they are held together by a mix of protein bonds that help give strength to the stratum corneum, which helps your skin form a protective barrier from the outside environment.
Once skin cells reach the outmost layer, they’re naturally shed away to make way for new cells. When we’re younger, new cells reach the surface every two to three weeks. However, as we age, the cell regeneration process takes longer—from six to eight weeks for mature skin.
When skin cells aren’t shed frequently enough, your complexion can begin to appear dull and dry. Additionally, the accumulated dead skin cells can lead to clogged pores and blemishes.
AHAs work to detach dead skin cells by loosening the sticky, glue-like protein bonds that hold them together. This allows dead skin cells to fall away easily, revealing the brighter, healthier skin beneath.
In addition to helping to unglue dead skin cells, several studies have shown that AHAs can aid in increasing your skin’s thickness, improving collagen density and the quality of the elastic-like fibers that give you skin the ability to “bounce back” and remain supple , ,  & .
Choosing an AHA
Because alpha hydroxy acids have humectant properties, meaning that they attract and hold moisture close to the skin’s surface, they’re a preferred chemical exfoliant for those who struggle with dryness.
AHAs are most commonly found in the following three forms: glycolic, lactic, and mandelic:
Glycolic Acid: This is the most common of AHAs. Glycolic acid has the smallest molecular structure, which means it can be the most effective, but also has the potential to be the most irritating to sensitive skin types. If you are new to AHAs and shopping for a glycolic acid product, start slow with a lower percentage, typically eight to ten percent. Additionally, glycolic acid has mild humectant properties, which help to draw moisture to your skin’s surface.
- Lactic Acid: Lactic acid is the second most common AHA. Derived from milk, its molecular structure is larger than that of glycolic acid, but not as large as mandelic. Lactic acid products are generally recommended for sensitive skin types, particularly those who struggle with rosacea. It is highly humectant, making it a top choice for those who struggle with dry skin.
- Mandelic Acid: This is the least common form of AHA. However, because mandelic acid has the largest molecules, it’s the least irritating. It has moderate humectant properties, lending a moisturizing effect without leaving normal skin feeling overly oily. Mandelic acid is also an antibacterial and an anti-microbial—making it the best choice of the three AHAs for acne-prone skin.
How to Use Your AHA Product?
AHAs are water-soluble, which means that they work best on bare, clean skin. To use an AHA to your best advantage, wait at least ten minutes after patting dry before applying the AHA product. If you use an oil cleansing method instead of standard cleanser and water, it’s recommended that you wipe away as much of the oil residue as possible before applying an AHA.
How to work an AHA into your existing skin care routine? Just follow this order:
- Cleanse your skin with your preferred cleanser
- Pat dry
- Apply a toner
- Apply your AHA product
- If you use a serum, apply it immediately after the AHA product
- Finish with the moisturizer of your choice
AHAs are photoreactive, meaning that they should only be applied at night. However, if you’re applying an AHA as part of your routine, don’t forget sunscreen! AHAs increase your skin’s photosensitivity, meaning that you’ll be far more likely to burn than you would normally—damaging all those freshly revealed skin cells.
Because skin is so much more susceptible to sun damage when AHA is part of your routine, we highly recommend picking a sunscreen that’s stable. This means the UV filters used in a formula don’t break down or degrade when exposed to light.
Which sunscreens are stable? Those that include physical sunblocks, such as titanium dioxide or zinc oxide.
While physical sunscreens might bring to mind those sticks of white zinc mom used to smear on your face before heading to the beach, rest assured that formulas have come a long way in the last decade.
My personal favorite physical sunblock is made by EltaMD, which was recommended by my dermatologist for use with AHA products. The brand offers both clear and tinted formulas. Those with normal or oily skin might find that it’s a bit heavy, especially in a humid climate. However, that sure beats a sunblock that makes you look like Casper.
If you’re new to making the switch to a physical sunblock, do be prepared to start using a separate makeup remover—these formulas generally have major sticking power.
If you’re new to using an AHA product, introduce it into your skin care routine slowly—beginning with three times a week until you build up a tolerance.
Final AHA application tip? While my experience might be singular to my specific AHA product, made by Acne.org, I noticed that regular use caused my skin to start bleaching fabrics. Not only pillowcases and towels were at risk either. Because I applied AHA on my throat and chest, even blouses were accidentally bleached until I figured out that wearing an undershirt could reduce contact and save my dwindling wardrobe.
Beta Hydroxy Acids (BHAs)
Where AHAs work to unglue dead skin cells, BHAs “de-gunk” pores. This makes beta hydroxy acid products a primary choice for oily and acne-prone skin—though a combination of AHA and BHA products is especially beneficial for combating acne.
In terms of cosmetics, BHA refers specifically to salicylic acid, which is derived from salicin—the same anti-inflammatory agent that’s found in aspirin. Those with aspirin allergies should avoid BHA products.
Unlike AHAs, salicylic acid isn’t a humectant. And, while it’s gentler than other acne-fighting ingredients, such as benzoyl peroxide, salicylic acid is still known to dry out your skin.
How to Use Your BHA Product?
Adjusting your skin care routine to include a BHA can be done in the same order as inserting an AHA product—with one exception. That’s because salicylic acid is oil soluble, you don’t need to wait ten minutes after patting dry to ensure that there’s no moisture left.
Similar to AHAs, start slowly when introducing a BHA product into your skin care routine. If you use too much, too fast, your skin might start to feel excessively dry and crack, making you feel like piling on excess moisturizer, which could lead to more clogged pores.
Unlike AHAs, beta hydroxy acids are not known to make your skin more sensitive to the sun . While you should still use sufficient sun protection every day, there’s no need to up your coverage with BHAs, or to choose only stable sunscreens.
Choosing a BHA
When searching Reddit’s Skincare Addiction forum, which I’ve found to be chock full of helpful reviews, the most commonly recommended BHA product are the Stridex Triple-Action Alcohol Free Pads.
However, some reviewers have expressed sensitivity to the inclusion of menthol in Stridex’s formula. The runner up product is made by Paula’s Choice—Clear Regular Strength Anti-Redness Exfoliating Solution With 2% Salicylic Acid.
Want the Benefits of Both AHA & BHA?
To refresh your memory, here’s a quick recap of the benefits provided by AHA and BHA products:
Alpha hydroxy acids work by ungluing the matrix of protein bonds that keep dead skin cells stuck to the surface of your epidermis. High in humectant properties, AHAs attract and hold moisture next to your skin, making them a top choice for those struggling with dryness. This ingredient does cause photosensitivity, but is also preferred to combat the effects of sun damage. Best for use at night only, and requires a stable sunscreen each morning.
Beta hydroxy acid, essentially salicylic acid, is best for oily skin types, as it works to penetrate pores and removing sebum. While salicylic acid can be drying, it doesn’t make your skin more sensitive to the sun. This means that BHA products can be used both morning and night, once you’ve built up a tolerance.
If you’d like the benefits of both AHA and BHA products, it’s possible to incorporate both into your skin care routine. However, we advise taking it extra slow, picking one type of chemical exfoliant first and building up a tolerance before adding the second. Additionally, those with sensitive skin should proceed with extreme caution.
Have you had success incorporating an AHA or BHA product into your skin care routine? We’d love to hear about your experiences in the comments below.
More on Exfoliants:
- Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study
- A review of skin ageing and its medical therapy
- Epidermal and dermal effects of topical lactic acid
- Glycolic Acid Treatment Increases Type I Collagen mRNA and Hyaluronic Acid Content of Human Skin
- The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin