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AHA, BHA, PHA and LHA: What are they and how should they be used?

A guide to using AHA, BHA, PHA and LHA ingredients

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AHA, BHA, PHA and LHA: What are they and how should they be used?
Written byPippa HarmanCo-Founder Renude
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Alpha hydroxy acids (AHAs), beta hydroxy acids (BHAs) and polyhydroxy acids (PHAs) are types of acid found in many chemical exfoliants. They help to remove dead skin cells from the top layer of your skin, but they work in different ways and each has their own additional benefits.

  • AHAs work on the surface layer of the skin to dissolve dead skin cells, which in turn can even skin tone, improve radiance and target fine lines - some also have hydrating properties. 
  • BHAs, (better known as salicylic acid), have antibacterial properties and are oil-soluble, so can sink deeper into the skin to unclog pores, dissolve excess oil and prevent blackheads and breakouts.
  • PHAs have a larger molecular structure than AHAs and BHAs, which means they take longer to penetrate and won’t penetrate as deeply, working on the surface layer of the skin and therefore more suitable for sensitive skin.

AHA, BHA and PHA ingredients you may be familiar with:


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


  • Salicylic acid (or related ingredients like willow bark extract)

It’s relevant to mention here that Lipohydroxy Acids (LHAs) are becoming a hot topic of conversation and whilst LHA is a “derivative of salicylic acid" it is much gentler than a BHA and can be used more often than AHA and BHA but will work much slower. 


  • Gluconolactone
  • Lactobionic acid
  • Maltobionic acid
  • Galactose

It’s important to note that due to their exfoliating nature, any form of acid may irritate your skin, bring on redness, or make you more likely to get sunburnt, so it’s important to choose the right product for your skin and introduce it as directed. That being said, if you have very sensitive and reactive skin or plan on going away any time soon, it might not be the best time to introduce an AHA or BHA product into your skincare routine.

It’s always a good idea to talk to our aestheticians before you introduce any new product. They can let you know if it’s right for you, whether it could affect the success of your current routine and what strength or concentration of the ingredient is best suited to your needs.

Using AHAs, BHAs and PHAs Together 

These acids are used for treating different skin challenges and are often suitable for different skin types. AHAs might be best for less congested skin, looking to improve radiance and even tone, whereas BHAs tend to work best for those with oilier skin that’s prone to congestion. While PHAs are better for sensitive skin types. 

More frequently, we’re seeing products using a combination of either AHA and BHA or AHA and PHA together. If you think you might benefit from different aspects of these ingredients, choosing a carefully formulated combination product is less risky than mixing and matching different exfoliating acids on your own in terms of skin irritation.

Understanding which exfoliant is right for you (if at all) can be confusing and when not used correctly or with the wrong products, can lead to skin damage. If you’re unsure, speak to one of our skincare specialists before you introduce any new products into your routine. They’ll be able to advise which acid type is best for you and your skin goals and how to incorporate it into a routine. 

If a product with AHA, BHA or PHA is advised, it’s important to follow instructions carefully. Usually, this would be to phase the ingredient into your routine, using 1-2x per week initially and building up over several weeks to daily use (as a maximum). 

We see so many different crazes and miracle ingredients out there that it’s hard not to want to try it all, but overuse of any acid can really affect your skin barrier health over time. If your skin starts to feel red, dehydrated, irritated, or itchy or you see sudden breakouts at any point during the use of exfoliants, it’s important to reduce or stop the use of any active ingredients and focus on healing the skin barrier. Sometimes it’s better to keep your skincare simple. 

How to Use AHAs, BHAs and PHAs Safely

Take some simple steps to protect your skin:

  • Introduce AHA and BHA slowly – your skin is always changing and will build up a tolerance, so start with a small amount of product, 1-2 times per week. This will be enough for your skin to get familiar with the ingredients.
  • PHA products in general, can be safely used 3-4 times a week since they are more gentle than other acids. That being said, please keep in mind, that the right amount depends on your individual skin type and the other products in your routine. Follow the recommended use and try not to be tempted into using more than you need. Our aestheticians will let you know how often and how much of the product to use.
  • Use an SPF on your face every single day (yes, that’s right) after your moisturiser, even if you are spending the day indoors. UVA and High Energy Visible light can penetrate through windows, so daily protection is a must! 
  • If your skin tends to be reactive, do a patch test before use. Put a little bit of the product on a small area of your skin first (behind the ear or inner wrist.) If your skin is fine 24 hours later, you can proceed to use the product as advised. If you notice any type of reaction (look out for heat, redness, itching, irritation and so on), avoid using the product and speak to our skin specialists.

What a Dermatologist says: 

Dr Justine Kluk, our consultant dermatologist, has her own, respected clinic on Harley Street and specialises in treating acne. Due to this she is also familiar with using acids and recommending the right one for all kinds of skin. 

“Exfoliating acids have become increasingly popular with skincare enthusiasts and those looking to improve their skin over the last couple of years. They are also one of the areas where there is most confusion. Potential pitfalls are being overzealous when starting out (too much too soon) and not being cautious about combining with other active skincare ingredients. 

My top tip: read this blog, go slow when starting out and keep the rest of your routine gentle and simple.

Why are PHAs better for sensitive skin than BHAs or AHAs?

PHAs help to hydrate skin and boost skin cell regeneration. Compared to the other exfoliating ingredients, they’re typically less irritating, especially if you have sensitive skin. PHA molecules are larger in size and therefore don’t penetrate as deeply as AHAs when applied to the skin. They may take longer than AHAs and BHA for visible results because of this, so do be prepared to give it a little time. It may be best to think of progress as a marathon rather than a race.

PHAs can also be used during pregnancy if needed, and are a nice option for congested spot-prone skin, as they help even out texture as well as tone.

Should I be using LHA or PHA for sensitive skin?

Both PHA and LHA are useful for people with sensitive skin because they are gentler and work slower than AHA and BHA. However, PHA is preferred by those with dry skin, or with rosacea or eczema because of its larger molecular structures that work only on the surface layers of the skin, making it more gentle. PHA also retains moisture and can provide visible improvements in sun-damaged skin. 

LHAs are oil-soluble so are best suited for combination or oilier skin types, prone to congestion. Due to their oil-soluble nature they may be too stripping for drier skin types, as they will dissolve the natural oils within the skin. This being said, it does depend on the specific formulation, so if in doubt we’d always recommend speaking with an aesthetician to choose the best option for you based on its capability to fit into your routine around other ingredients. 

Take our skin health quiz as a first step in receiving your personal routine and even book in to speak to one of our aestheticians at a time that suits you.


AHA and BHA for Skin: What to Know ( 

AHA vs BHA: The difference and how to use both (

AHA and BHA – What Is the Difference and How to Use Them in Skincare (

AHA vs. BHA: Choosing an Exfoliant, Acid Types, Products (

Pippa HarmanCo-Founder Renude
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Pippa HarmanCo-Founder Renude
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