AHAs vs. BHAs vs. PHAs

Alpha-hydroxy acids (AHAs), beta-hydroxy acids (BHAs), and poly-hydroxy acids (PHAs) are the secret skincare weapons you didn’t know you needed. All three are exfoliants, but not the gritty kind that involve you rubbing your face and body with sugar in the shower.

No, these are chemical exfoliants that penetrate the skin, remove dirt and dead skin cells, and leave you with a radiant, healthy complexion. Sounds pretty, great right? The tricky thing is knowing which acid to use when. That is why we’re breaking down the differences between AHAs, BHAs, and PHAs, including what they are, the benefits of each, and when and how to use them. 


What are AHAs?

Alpha-hydroxy acids are acid/chemical exfoliants that include the likes of glycolic acid, lactic acid, malic acid, citric acid, and tartaric acid. This group of acid compounds is most commonly derived from plant-based sources. For example, glycolic acid (the most popular AHA) comes from sugarcane, citric acid from lemons, and malic acid from apples. Although they are all chemical exfoliants and offer surface-level exfoliation, the molecules of each differ in size which means they differ in potency. As such, they can’t be used interchangeably, so you should always pay attention to which AHA(s) a skincare product contains.


What are the Benefits of AHAs?

  • Hydration: Like glycerin or hyaluronic acid, certain AHAs are actually humectants, which means they retain water, adding a major boost of hydration to the skin. If you’re looking to revive dry skin, consider adding glycolic acid, malic acid, or lactic acid to your routine. 
  • Stimulate Collagen Production: While you might be inclined to think AHAs are all about surface-level exfoliation, they do have the ability to penetrate deeper into the skin and stimulate collagen production. To boost collagen production and enjoy a plump, wrinkle-free complexion, there’s no AHA better than glycolic acid.
  • Surface Exfoliation: As mentioned above, AHAs are at their core, exfoliants. That’s why you can expect some serious exfoliation from almost any AHA you choose. AHAs work to dissolve the “glue” that holds together dead skin cells, removing them and leaving you with smooth, radiant skin. AHAs offer a gentle alternative to physical exfoliants, like scrubs, which makes them ideal for those with sensitive skin.

  • What are BHAs?

    Beta-hydroxy acids, or BHAs, have a reputation as acne saviours. This is because the most common BHA on the market, salicylic acid, has long been hailed as one of the most effective acne-fighting ingredients. Unlike AHAs, BHAs are oil-soluble, making them an excellent choice for those with normal to oily skin, who frequently suffer from breakouts and blemishes. Like AHAs, BHAs are gentle chemical exfoliants, which also makes them suitable for sensitive skin.


    What are the Benefits of BHAs?

  • Penetrates Pores: The most prominent benefit of BHAs is that they have the ability to penetrate deep into the pores. Since they are oil and fat-soluble, BHAs like salicylic acid work not only on the skin’s surface but deep into the pores, removing dead skin cells and promoting healing.  
  • Calming: BHAs have natural anti-inflammatory powers, which also makes them ideal for fighting acne. Beyond removing dirt and debris that has built up on the skin’s surface and clogged pores, these acids can soothe and calm the skin. This helps with reducing the redness or irritation that often comes with acne. Even if you don’t suffer from acne but you do suffer from redness or rosacea, BHAs can help.
  • Antibacterial: Finally, BHAs contain antibacterial properties, which work to speed up the healing of wounds. This makes them a go-to for getting rid of acne fast, but they can also be used to treat calluses and even warts. Owing to how deeply BHAs penetrate the skin, they can fight bacteria on a level that other exfoliants simply can’t. 

  • What are PHAs?

    If you’re into skincare, then AHAs and BHAs probably aren’t anything new, but PHAs you may have never heard of. That’s because they’re the new kids on the block. Poly-hydroxy acids, or PHAs, fall within the AHA family but they have some key differences that warrant their own category. Like AHAs and BHAs, they are exfoliants, however, their molecules are much larger in size compared to AHAs. Two of the most common PHAs are gluconolactone and lactobionic acid, and while their skincare benefits are similar to that of AHAs, they are even gentler than their alpha cousins.


    What are the Benefits of PHAs?

  • Gentle, Non-Irritating: Think of PHAs as the gentle giants of the acid compound family. Due to the large molecules they contain, they can’t penetrate the skin’s surface, which makes them a lot gentler on the skin. It also means they take longer to sink in, so don’t apply more products on top of a PHA right away. Given the fact that they only work on the skin’s surface, they are generally non-irritating, which means you won’t experience that tell-tale stinging sensation associated with BHAs like salicylic acid.
  • Moisturizing: Like many AHAs, PHAs are humectants, which means they retain water and keep skin moist. If you suffer from dry skin or are in the middle of a harsh winter, PHAs will help revive a dull complexion, making it plump and hydrated once again.
    • Anti-Inflammatory: PHAs are chock full of anti-inflammatory properties, meaning they not only moisturize and exfoliate the skin but they also soothe it. And given how gentle they are, PHAs are suitable for anyone with sensitive skin, including those who suffer from redness, rosacea, or eczema. 

    When to Use AHAs vs. BHAs vs. PHAs


    Reach for AHAs if:

    • You have dry skin: As humectants, AHAs will draw in moisture and revive dull, dry skin.
    • You have fine lines and wrinkles: When it comes to anti-aging, AHAs are best. As humectants and collagen stimulators, they will plump the skin, reducing the appearance of fine lines and wrinkles. 

    Reach for BHAs if:

      • You suffer from acne: BHAs, owing to their impeccable ability to penetrate deep into the skin and unclog pores, are best suited to serious skin concerns, such as acne (including cystic acne). You’ll most often find BHAs in spot treatments, scrubs, cleansers, and toners. 
  • You suffer from inflammation or redness: Again, owing to how deeply BHAs penetrate, in addition to their anti-inflammatory properties, they are the best course of action if you’re looking to reduce redness or irritation. 
  • You have oily skin: As BHAs are oil-soluble, they will be able to penetrate and break down oil in order to exfoliate the skin underneath. AHAs are not oil-soluble, which means those with oily skin may have a more difficult time reaping the benefits that AHAs offer.

  • Reach for PHAs if:

  • You have sensitive skin: PHAs are by far the most gentle exfoliant in the acid family. Owing to the large size of their molecules, they aren't able to penetrate the skin’s epidermis, which means you don’t run the risk of irritation (this is also why it’s important not to apply another skincare product immediately after applying a PHA - give it time to its magic). 
  • You have dry skin: As part of the AHA family, PHAs are also humectants, which makes them ideal for people with dry skin. These water-loving acids draw in moisture to the top layer of the skin and help you retain it, for a plump, hydrated complexion. 

  • How to Use AHAs, BHAs, and PHAs Together

    AHAs, BHAs, and PHAs can be used in conjunction with amazing results, if you know what you’re doing. Too high a concentration of any acid can result in irritation, so we recommend starting off with a skincare product that already combines more than one type of acid exfoliant. AHAs and BHAs are the most common combination, available in serums, peels, masks, and exfoliants. 


    As the gentlest member of the acid family, PHAs can be combined with almost any other acid or skincare ingredient at large (in fact, many AHA-based skincare products already contain PHAs to clean up the surface-level debris that AHAs miss). But you can also combine PHAs with retinol for a serious acne treatment or with hydroquinone to help fade dark spots and fight aging. 


    If you do want to use each type of acid separately, start out by applying them on opposite days or on different parts of the face (for example, applying AHAs to dry areas and BHAs to oily areas).