AHAs vs BHAs

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I made a very (like yesterday) recent discovery – I’ve never written a post solely about the difference between AHAs and BHAs. I have, of course, discussed this in separate posts like my acid posts but nothing dedicated to it specifically. That horrified me for two reasons; when I was a skincare novice I didn’t fully understand and it took me a while to grasp what to look for when shopping skincare and two I get asked this all the time. Acid’s are such a complicated part of skincare and you have to be aware of what you’re putting on your skin before you delve into it. So, let’s go!

How do the structure’s differ?

First off, AHAs and BHAs are acronym’s for Alpha Hydroxy Acids and Beta Hydroxy Acids. In chemical terms these names are just an explanation of the structure of the molecule. It simply tells us that there is a Hyrdoxy (OH group, also known as an alcohol group) in the molecule and the acid part denotes a carboxylic ‘acid’ group (COOH for those of you who know your chemistry) present in the structure.

The alpha and beta part’s tell us where exactly those two groups are sitting within the molecule. An alpha molecule tells us that the OH and COOH groups are closer together than in a beta molecule. More specifically if the OH and COOH are one carbon apart it would be an alpha molecule and if they are two carbon’s apart it would be a beta molecule.

It’s actually quite hard to see the difference in a chemical structure if you’re not used to drawing them. Hence, I’ve refrained from drawing them. However, now that we know the chemical difference we can look at what make’s them unique when it comes to treating your skin.

The difference

AHAs are water soluble so only work on skin’s surface whereas BHAs work on skin’s surface and deep inside the pore because it’s oil soluble.

That means two things; it’s most often preferred for normal to oily skin prone to bumps, clogs, blemishes, and enlarged pores and it is thought to be the gentler of the two acids. It has been noted to have some natural skin-calming properties. Gentle enough for skin that’s sensitive or prone to redness or rosacea.

How AHAs and BHAs are Similar?

Now we understand their structure we understand that some of their functions must be similar because at the core of them they have two of the same functional groups. If this was your first thought you would be correct. They work to “unglue” the bonds holding dull, dead skin on the surface. Once those bonds are broken—gently and evenly—skin naturally sheds its spent cells. So, although you won’t actually see your skin exfoliating, you’ll soon see (and feel) the smoother, younger-looking skin. Hence, they are both considered chemical exfoliates because of their ability to shed the outer layer of skin.

Which one should you use?

AHAs can be used by everyone and are marketed that way too but if you have very dry or sensitive skin you will want to build up your tolerance by starting with use only once a week and/or starting with a low concentrated acid product. They are primarily used for:

  • mild hyperpigmentation like age spots, melasma, and scars
  • enlarged pores
  • fine lines and surface wrinkles
  • uneven skin tone

BHAs on the other hand, are mainly used for acne and sun damage, this is due to the calming nature attributed to them. These products go deep into your hair follicles to dry out excess oils and dead skin cells to unclog your pores. Because of these effects, BHAs are most suitable for combination to oily skin. if your concerns include reducing rosacea redness you may also have more success with BHAs.



Pixi Glow Tonic

Pixi Glow Glycolic Boost

Pixi Glow Tonic To Go

The Ordinary Glycolic Acid Toner

REN Ready Steady Glow Daily

Skinceuticals Glycolic 10 Overnight Renew Corrective Cream


Paula’s Choice Skin Perfecting BHA liquid Exfoliant

The Ordinary AHA and BHA Mask

Murand Age Reform AHA/BHA Exfoliating Cleanser

The Ordinary Salicylic Acid Solution

The Ordinary Salicylic Masque