Understanding Exfoliation: AHAs vs. BHAs

Chemical exfoliants are incredibly effective for sloughing away dead skin to reveal a smooth, even complexion. Most chemical exfoliants on the market are either alpha hydroxy acids (AHAs) or beta hydroxy acids (BHAs). Each type of acid has a unique function that works best for specific skin concerns — here’s the lowdown.

A woman with smooth skin who likely understands the difference between AHAs and BHAs for exfoliation

What are alpha hydroxy acids?

AHAs are naturally occurring substances found in fruits, milk and cane sugar. They are some of the gentlest, yet robust, exfoliants you can use on your skin. Common alpha hydroxy acids include:

  • Glycolic acid
  • Lactic acid
  • Mandelic acid
  • Citric acid

How do AHAs work?

Alpha hydroxy acids are water soluble chemicals that exfoliate the skin by gently loosening the surface layers of dead cells. Essentially, an AHA helps break down the loose bonds between our skin and its dead cells, allowing our body to shed them.

Though frequently misrepresented as skin-thinning, AHAs have actually been shown to promote thickness in the deeper layers of the skin. Generally, all skin types can use alpha hydroxy acids.

What skin conditions do alpha hydroxy acids treat?

AHAs have been shown to be beneficial in the treatment of:

  • Uneven skin tone and texture
  • Blemish scarring
  • Hyperpigmentation
  • Blemishes
  • Rough, bumpy skin (aka keratosis pilaris)

SLMD Glycolic Acid Body Scrub combines exfoliating granules with glycolic and lactic acids to slough away dead skin cells. It can help manage common skin conditions like keratosis pilaris, or ingrown hairs.

SLMD Glycolic Acid Body Scrub

    What are beta hydroxy acids?

    The term BHA almost always refers to salicylic acid, which was originally derived from willow tree bark. Unlike water soluble AHAs, beta hydroxy acids are oil soluble.

    How do BHAs work?

    While alpha hydroxy acids exfoliate by loosening dead skin cells, BHAs penetrate into pores to break up sebum and dead cells trapped inside. They are ideal to use as an initial step in a skincare routine, as they open pores up to receive other treatment ingredients. All skin types are typically fine using BHAs, with the exception of incredibly sensitive complexions.

    What skin conditions do beta hydroxy acids treat?

    BHAs are most commonly used to manage blemishes, as their function within the pore is to loosen the bacteria and debris that cause breakouts. SLMD Skincare Salicylic Acid Cleanser for face and Salicylic Acid Body Wash both thoroughly cleanse yet are gentle enough to be used daily. Though best known for treating blemish-prone skin, beta hydroxy acids have many benefits, including:

    • Clogged pores
    • Dullness
    • Fine lines and wrinkles
    • Sun damage

    Are AHAs and BHAs suitable for all skin types?

    Generally speaking, alpha and beta hydroxy acids are safe for all skin types. Those with more sensitive skin should start with lower concentrations, or formulas that rinse off (like cleansers) rather than remain on skin (like creams and lotions).

    As with other potent actives like retinol, when using AHAs or BHAs, your skin will be more susceptible to sun damage. While you should always be applying an SPF in the mornings, ensure you’re wearing at least an SPF 15 while using any alpha or beta hydroxy acid products.

    Dr. Lee’s last word

    Alpha and beta hydroxy acids are some of my favourite dermatological ingredients, because they’re incredibly effective exfoliants that can also be gentle on your skin. Glycolic acid (an AHA) excels at treating keratosis pilaris, while salicylic acid is my favourite for keeping pores clear to prevent breakouts.

    —Dr. Sandra Lee


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