WTF are... AHAs/BHAs anyway?
Like eyebrows, these guys are sisters, not twins
So… WTF is it?
AHAs and BHAs are 2 different types of chemical exfoliants.
They work in different ways and can be used individually or combined. Some products combine both in one handy bottle (you often have to shake the bottle before use in this instance).
How do you pronounce it?
I’m pretty sure you can figure this one for yourself.
But they stand for alpha-hydroxy acid and beta-hydroxy acid.
What’s the point of it? I mean, what does it actually do?
AHAs are water-soluble fruit or sugar-based acids. Those pineapple/papaya enzyme cleaners you’ve seen? They’re AHAs.
AHAs smooth dead skin cells from the surface of your skin, brightening and encouraging cell renewal.
Common AHAs are:
Glycolic acid (sugar-based)
Lactic acid (sugar/lactose-based)
Citric acid (I’ll give you 3 guesses. NB, this is not the same as Vitamin C)
Malic acid (from apples)
Tartaric acid (from grapes - Caudalie has a lot of these)
BHAs are oil-soluble and penetrate deeper into the skin layers to remove dead skin cells and excess sebum/oil/dirt.
Common BHAs are:
Salicylic acid
That’s pretty much it. There are a couple of other BHAs approved for cosmetic use, but the one in the bottle on the shelf is almost certainly salicylic acid.
How does it work?
AHAs penetrate the stratum corneum, which - AS WE KNOW - is the outermost layer of the epidermis. AHAs are acids and the acidity weakens the bonds between the dead skin cells (which are held together by desmosmomes1) and sloughs them off the outer layer of the skin. Yay!
BHAs also weaken the bonds/desmosomes, but within the hair follicles and pores, loosening trapped dead skin cells, debris, and sebum, unclogging them and helping to clear the complexion. Yay!
And why would someone want it?
The benefits of exfoliation are described here:
How much is it?
AHAs and BHAs can be bought very cheaply. The Ordinary, The Inkey and Superdrug all offer versions of salicylic, lactic and glycolic acid for under £11/$13.
There are also a bunch of K and J beauty combined AHA/BHA options.
As with everything in skincare, you’ll find someone willing to sell you these ingredients for £££, but if you’re dipping your toe in, start cheap.
Does it hurt?
As with all acid use at home - if you feel more than a momentary tingle/sting, either the product or your cleaning routine is too harsh for your skin.
Have I had it?
I’ve used AHAs and BHAs for years. Daily for at least a decade and before that, for years, less frequently2.
Would I have it?
I’m currently not using any AHAs/BHAs as I’m incorporating azelaic acid and retinoids into my routine and the use of AHAs/BHAs is contraindicated with this, especially during the introductory phase.
I would absolutely use AHAs and BHAs in the future, if needed, tolerated and appropriate.
Should you have it?
As long as you’re not using azelaic acid or retinoids, then AHAs and BHAs can usually be beneficial to your routine.
It’s unlikely you' need to use more than once a day, so if you have a day and night skin routine, that incorporates AHAs, I’d suggest you only use at night3.
You don’t need more than one product with either an AHA/BHA or both in, however. So if you looked down the list and realised that you’re layering on glycolic and lactic, or you have 2 products both with a high concentration of salicylic acid, you can almost certainly lose one of them.
Similarly, if you’re using a product that contains 2 AHAs as part of the formulation, it might be overkill and I’d suggest you try them separately and individually for a few weeks each, then decide which your skin likes better.
AHAs and BHAs can increase your sun sensitivity, so be cautious if you’re not applying SPF as part of your routine.
There was a school of thought that AHAs could worsen hyperpigmentation in darker skin tones, but Paula Begoun debunks that here. If it’s good enough for Paula, it’s good enough for me4.
Anything else I think you should know?
ONLY PROCEED IF YOU ALREADY KNOW THAT YOU ARE NOT SENSITIVE TO SALICYLIC ACID
I REPEAT: ONLY PROCEED IF YOU ALREADY KNOW THAT YOU ARE NOT SENSITIVE TO SALICYLIC ACID
Once more, because this is The Internet and people are sometimes ridiculous: ONLY PROCEED IF YOU ALREADY KNOW THAT YOU ARE NOT SENSITIVE TO SALICYLIC ACID
Before you spend a lot of money on a salicylic acid mask5, crush 8 aspirin tablets into a powder and mix with a half or whole tablespoon of any moisturiser that you fancy. Smear over your face - avoiding the eye area - and leave on for 3-30 mins, depending on how much time you have, and then rinse off throughly.
YOU ARE WELCOME.
Disclaimer: ‘WTF is…’ guides are intended to be a 3-5 minute introduction to a topic. They are, by their nature, not exhaustive.
If you have a concern that I’ve irresponsibly included/omitted information, don’t hesitate to get in touch to let me know and I’ll take a look.
Reminder that any cosmetic work undertaken should be in accordance with The 6 rules of cosmetic work. Here they are, in case you missed them the first time…
SCIENCE.
Because I was inconsistent and a bit grubby until my mid-30s
Because of the sun sensitivity potential and also because generally a night time routine can take longer than a morning routine.
Even if I do think her salicylic acid is overpriced.
It won’t ‘cure acne’, which I now realise the skincare lunatics on TikTok are peddling, but it is a v straightforward and cheap smoothing mask for most skin types.