Understanding Acids in Skincare – AHAs and BHAs

Understanding acids in skincare
Understanding acids in skincare. Photo by July Prokopiv


Are you confused by acids, how to use them and what to look out for? It is important to exfoliate skin and acids are one way to introduce exfoliators into your routine. Not everybody’s skin can tolerate acid – particularly those with extremely dry or sensitive skin – and some like our Founder can’t use them without ending up with red patches and hypersensitive skin. Today we’re looking at the role of two of the most commonly used acids in skincare – AHAs and BHAs – and giving you our top 5 tips for using them safely and effectively…



Alpha Hydroxy Acids (AHAs) and Beta Hydroxy Acids (BHAs) are both chemical exfoliators which are found in many skincare products, not just exfoliators and peels. AHAs are typically derived from fruits, sour milk and sugarcane and BHAs from willow bark and citrus fruits. In short, AHAs tend to work on exfoliating the outer layers of the skin while BHAs penetrate deeper. Below we’re unveiling how each acid works and the concentrations to look for in at-home use products that will not leave skin worse off…



The most common AHAs used are glycolic acid and lactic acid. These acids can be naturally occurring or synthetic, and work by removing the dead skin cells and debris from the skin’s surface to allow skin regeneration – the process responsible for a brighter, healthier and smoother complexion. They also help to reduce fine lines, dark spots and acne scars.

It’s important to note that acids come in varying strengths, so depending on the concentration, it may just remove the dead skin cells from the surface or the whole outermost layer; both of which can leave the skin more vulnerable. Around 4% is considered a low concentration for an at-home use AHA while up to 70% can be found in peels used by dermatologists. Glycolic acid, which is found in a number of peels as well as daily-use skincare products, is able to penetrate the skin better than lactic acid, although the latter is milder so is less likely to cause irritation.


You might also like to read: How Plant Oils Strengthen The Skin Barrier – Part One



BHAs go deeper into the pores of the skin and the oil glands, dissolving the mix of sebum and dead skin which can lead to breakouts. They also have collagen-boosting, anti-microbial and anti-inflammatory properties so can help treat acne, blackheads/whiteheads, reduce pigmentation, keep skin supple and calm any redness or inflammation. The most common BHA is salicylic acid which is derived from aspirin meaning unfortunately it’s unsuitable if you have an allergy to this. It’s also rather drying, so if using at-home, look for one with a concentration of around 0.5 – 2%.

There are products which contain both acids that can be used to exfoliate the skin more thoroughly and these can cause severe dryness and irritation, especially when used too frequently and in higher concentrations.



  • Always do a patch test. We advise doing this for all skincare/haircare before using for the first time, but it’s especially important for anything containing AHAs/BHAs. Peels may not be suitable for sensitive skin so doing a patch test helps you to identify if you will have a negative reaction. Not sure how to do this? The Ordinary have a great guide which covers how to do a patch test for a variety of products.
  • Introduce into your routine gradually. Start slowly with just one application a week and then a few times a week until your skin gets used to it. Then alternate between the two – weekly or a few times a week – but always observe how your skin is reacting.
  • Remember to apply SPF daily as photosensitivity is increased making the skin more vulnerable to sun damage and pigmentation after using AHAs/BHAs.
  • Steer clear of hot baths, perfumed skincare and other potent ingredients. Shortly after use, your skin may feel sensitive, so we recommend avoiding anything perfumed or with ingredients such as vitamin C, retinol and exfoliants. If your skin remains sensitive for more than a few hours then consider stopping using the acid until it feels stronger again.
  • Do not overuse. These acids can leave the skin red and dry, and cause pigmentation, premature ageing and thinning of the skin. If you want to use acids, then we recommend going to a dermatologist rather than using the at-home ones, to avoid overuse resulting in your skin looking and feeling worse off.
  • Do not mix actives. Be mindful of the actives that are in each of the products you are using, specifically serums and moisturisers, as some are not meant to be mixed. For example, mixing AHAs/BHAs and Vitamin C – the acids will destabilise the pH of the vitamin C rendering it ineffective. These combined can also dry out skin and exacerbate sensitivity. Similarly, retinol and AHAs should not be mixed as these can leave your skin vulnerable to UV rays.


You might also like to read:

Best Natural Face Exfoliators For Sensitive Skin

How To Make The Most Of Hyaluronic Acid

Layering Your Skincare For The Best Results



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