You may have seen the terms 'AHA' or 'BHA' sprinkled across your skincare products, but do you know what they actually mean?
Alpha hydroxy acid (AHA) and beta hydroxy acid (BHAs) are types of active skincare ingredients that exfoliate away dead skin cells. Despite sharing the same goal, so to speak, they have some key difference as well.
Here we explore AHAs vs BHAs, their different benefits and how to use them in your skincare routine.
What are AHAs and BHAs? An overview
Both alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) are naturally occurring chemical compounds commonly used in skincare products (although the ingredients in your skincare are often produced synthetically).
Both AHAs and BHAs are both adored for their anti-ageing properties. They are types of chemical exfoliants, applied topically to help rid your face of old and dead skin cells.
Despite both being used for exfoliation, different types of acids in the AHA and BHA families can target different skin concerns, and work better for different skin types.
You can find AHAs and BHAs in a variety of skincare products, such as skin peels, moisturisers, serums, cleansers, toners, and more.
What are AHAs?
AHAs are chemical compounds traditionally found in fruit, dairy or sugar cane*. For the purpose of skincare, AHAs (and BHAs) are chemical exfoliants, helping to shed dead skin cells and aid in skin cell renewal.
If you're wondering exactly how AHAs do this, they dissolve the adhesive that bonds your skin cells together, allowing dead cells to slough away. In turn, this stimulates collagen production and skin cell renewal, helping the skin appear younger, smoother and firmer.
AHAs are also humectants, i.e. they help retain moisture in the skin.
AHAs treat a range of skin concerns related to ageing and acne, including:
- Evening out skin tone (diminishing age spots, hyperpigmentation and discolouration)
- Smoothing the skin and improving skin texture
- Brightening skin tone
- Decreasing inflammation
- Reducing pore size
- Reducing and preventing fine lines and wrinkles, and
- Treating acne.
*Despite naturally occurring as fruit acids, chances are the AHAs in your skincare products were synthetically produced.
What are BHAs?
BHAs are also a chemical exfoliant, working to break down dead skin cells. However, BHAs are more suitable for folks with oily or combination skin. BHAs are oil or lipid soluble and are able to penetrate your skin's oily surface in order to get into those pores and, essentially, clear them out.
Thanks to anti-inflammatory and anti-bacterial properties, they're particularly great for those with acne-prone skin.
BHAs offer most of the same benefits as AHAs, but can also:
- Penetrate more deeply, passing through oil and sebum on your skin to get into your pores
- Help fight acne (AHAs can do this to an extent, but BHAs are better for existing spots and can get deeper into the skin, rather than exfoliate the surface)
- Unclog pores, making them appear smaller.
The difference between AHAs vs BHAs
A key difference between AHAs and BHAs is that most AHAs are water soluble, while BHAs are oil soluble. AHAs can easily penetrate the surface layer of the skin, while BHAs are able to penetrate deeper, below your skin's oily surface.
AHAs are better for normal skin types. The chemicals can be irritating to sensitive skin, especially if you're yet to build-up a tolerance. However, there are some AHAs that are mild enough to be enjoyed by those with sensitive skin.
BHAs tend to be better for oily and sensitive skin types. They may also be preferred by folks with darker skin, who may be prone to hyperpigmentation or discolouration.
When it comes to AHA vs BHA, neither is objectively better nor worse — this will depend on your skin type and the skin concerns you want to address.
Types of AHAs
Alpha hydroxy acid (AHA) is an umbrella term to describe a range of different water-soluble acids. These include:
Of all AHAs, glycolic acid has the lowest molecular weight, meaning it sinks easily into the skin. This can also make it one of the more potent AHAs, which can be irritating to sensitive skin.
Glycolic acid is usually available in over-the-counter skincare products in concentrations of 10 per cent or less. However, it can be used in higher concentrations by cosmetic professionals, such as in a chemical peel.
NOTE: With all acids, remember more does not necessarily equal better — especially when it comes to the concentration of an active ingredient. Depending on your age and experience with this ingredient, start with a lower concentration and build from there. Also, don't forget to patch test first!
Lactic acid is derived from milk and provides similar benefits to glycolic acid. However, lactic acid is much milder and therefore likely to be more suitable for folks with sensitive skin.
It has even been praised for its moisturising and antioxidant effects.
Lactic acid is available in a range of concentrations, with beginners and those with sensitive skin encouraged to start with five per cent.
Malic acid — naturally found in apples — is very mild and, therefore, great for sensitive skin. However, even though it will still exfoliate dead skin cells, it is much less effective than lactic and glycolic acids.
Malic acid is not commonly used as a primary ingredient in skincare. You're more likely to see it alongside another AHA or BHA to improve or balance their performance. Check the ingredients list on your products to see if it's in the mix.
Mandelic acid is derived from almonds and offers another alternative to glycolic or lactic acids for those with sensitive skin.
It is exfoliating, anti-inflammatory and comedolytic (helps prevent blemishes). Unlike other AHAs, mandelic acid is lipid soluble as well as water soluble, making it a more effective acne treatment.
Tartaric acid is derived from grapes and is even milder than the aforementioned acids.
It doesn't have the same exfoliating strength and is not typically used for this purpose alone. Instead, tartaric acid is added to a skincare formula to help maintain healthy and effective pH levels that won't damage your skin barrier.
Citric acid is derived from, you guessed it, citrus fruits. It can also help remove dead skin cells but is so mild that it isn't used as a major exfoliant ingredient. Citric acid is more commonly used as a stabiliser.
Types of BHAs
Beta hydroxy acids (BHAs) is an umbrella term used to describe a range of oil soluble acids. These include:
Salicylic acid is the most common of the BHAs. It helps to exfoliate and unclog the pores, clear away bacteria and reduce the formation of blackheads and whiteheads. If you have oily or acne-prone skin, you're likely to have more success with salicylic acid than AHAs.
Thanks to its ability to penetrate sebum and sink deeper into your skin, plus its anti-inflammatory and antibacterial properties, it's a must-have ingredient for anyone struggling with breakouts.
Salicylic acid is derived from willow bark.
When people talk about BHAs, chances are they're speaking about salicylic acid. It is the key BHA ingredient in most skincare. However, there are other BHAs, such as Beta-hydoxybutanoic acid, tropic acid and trethocanic acid.
Software's very own Salicylic Acid Foaming Wash combines the dual action of BHA and Poly Hydroxy Acid (PHA), which enables multi-layered penetration of the skin, leaving the skin exfoliated but not stripping the skin of its important oils.
It's perfect for those with acne-prone skin, helping to clear away dead skin cells and help prevent the formation of blackheads and whiteheads, and can also be used by those with sensitive skin thanks to the unique blend of low-irritancy surfactants.
How to apply AHAs
Due to the harsh nature of AHAs, it's better to avoid using them daily, especially if you're only starting your AHA journey and your skin hasn't had a chance to build a tolerance.
Beginners should start with a low concentrate (around five per cent for glycolic and lactic acids), patch test and then continue with use every other night or even as little as once a week for the first few weeks.
If you're using an AHA cleanser, as opposed to a peel, serum or moisturiser, you may be able to use it more frequently.
When it comes to any exfoliant, it's always better to use them at night to avoid any adverse affects from sun exposure during the day. Even if you've used your AHA at night, always apply an SPF during the day, especially the day after using an AHA.
You should also consider if your AHA is compatible with other ingredients in your skincare routine. For instance, avoid using AHAs with vitamin C, retinol or other exfoliating products. (FYI, you can use AHAs and BHAs together in some instances. More on that below.)
How to apply BHAs
You should be able to use salicylic acid every night but, as with AHAs, start slowly and patch test if just starting out. In the case of Software's Salicylic Acid Foaming Wash, we recommend using this two to three times a week to give your skin a break.
It's also recommended to wear sunscreen after using a BHA. Even though it's a milder, it is still an exfoliant that exposes immature skin cells to the elements!
No-no combinations are similar for both AHAs and BHAs: meaning, avoid vitamin C and retinol in conjunction with your BHA. BHAs can come in cleansers, toners, serums, moisturisers, sunscreen and more.
Can you use AHAs and BHAs together?
There are products on the market that contain both AHAs and BHAs, and these ingredients are generally safe to use together (in low doses). However, in reality, you shouldn't need to use both if you're using the right product for your skin.
AHAs and BHAs do the same thing ‚Äî exfoliate! Your skin type will tell you if you could benefit more from an AHA vs BHA, and a bit of research will guide you towards other ingredients and products you should add to your skincare routine.
Risks of AHAs and BHAs
Chemical exfoliants can leave users vulnerable to sunburn and skin damage if used incorrectly. AHAs, in particular, can be quite harsh on the skin.
When overused — either in too-high volumes or without adequate aftercare — AHAs can shed more skin layers than desired, resulting in the exposure of immature skin cells which aren't equipped to handle exposure to the sun or other environmental factors.
This can have the opposite effect than desired, potentially damaging the skin, causing redness, peeling, flaking, discolouration and burning.
It is always recommended to patch test any skincare product before full use. Also, remember to slip, slop, slap and try to avoid using acid peels and exfoliants before spending time in the sun.
- WILLIAMS, R.J.E. The Use and Safety of Hydroxy Acids in Cosmetics, Australian Society of Cosmetic Chemists (ASCC), 2005.
- National Centre for Biotechnology Information, Glycolic Acid, PubChem Compound Summary, 2022
- ALGIERT-ZIELINSKA, Barbara et al. Lactic and lactobionic acids as typically moisturizing compounds, International Journal of Dermatology, 2019
- TANG, Sheau-Chung, YANG, Jen-Hung, Dual Effects of Alpha-Hydroxy Acids on the Skin, Molecules Vol. 23, 2018
- National Centre for Biotechnology Information, Salicylic Acid, PubChem Compound Summary, 2022
- National Industrial Chemicals Notification and Assessment Scheme, Glycolic Acid, Priority Existing Chemical Assessment Report No.12, 2000