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AHAs and BHAs: what’s the difference?

AHA or BHA? If you're wondering which acid to reach for, we reveal the differences and the benefits

What’s the big deal about AHAs and BHAs? Are they really better at exfoliating than your fail-safe scrub? Everyone’s skin benefits from regular exfoliation, especially as we age and our skin’s renewal process starts to become more sluggish.

But if just hearing the word exfoliant makes your sensitive skin flushed with fear, you should know that you don’t need to rely on harsh, gritty formulations to get results.

In fact, over-zealous exfoliation can actually damage the skin’s top layer, cause inflammation and play havoc with its barrier function.

You know that grainy scrub lurking at the back of your bathroom cabinet—the one with a tendency to scratch and leave you looking rather pink?

Well, now’s the perfect time to introduce it to the bin and give your skin a high-tech helping hand instead with AHAs and BHAs.

If you’re unsure which is suitable for your skin type or condition, read on to discover the right acids for you.

What are AHAs?

AHAs (alpha hydroxy acids) are naturally derived organic acids that primarily work as exfoliators. These sophisticated active ingredients work by dissolving the bonds between skin cells and prompting the top layer of dead cells to shed while also promoting cell turnover.

This means that you don’t have to physically scrub the skin with granule-based products to get your glow on.

The most popular AHAs include:

  • Glycolic acid: Derived from sugar cane, glycolic acid molecules are small in size so are able to penetrate the skin effectively and deeply. Glycolic acid is normally the active ingredient found in clinic peels; you’ll also find it in countless home use retail products. 

  • Citric acid: Derived from citrus fruits like lemons or limes, citric acid is often used to adjust a product’s pH to prevent it from being too alkaline. It is also effective at exfoliating, improving elasticity and thickening skin. 

  • Lactic acid: Derived from lactose, lactic acid is very effective at treating hyperpigmentation and age spots. A gentle exfoliant, it’s ideal for sensitive skin and those prone to acne and pigmentation. It also works to pull water into the skin and prevent congestion.

  • Malic acid: Malic acid is derived from apples and pears, and can help to brighten skin by gently exfoliating and promoting cell turnover. With a larger molecule size than other AHA’s, it’s a great option for those with sensitive or acne-prone skin. 

  • Mandelic acid: Mandelic acid is derived from bitter almonds and packs a gentle punch, swerving irritation or redness. Ideal for acne sufferers and those with pigmentation and fragile skin, its’ molecule size is twice as big as glycolic acid. The acid of choice for darker skin, it’s also very effective at strengthening and brightening.

What are the skincare benefits of AHAs?

Tolerable by most skin types, reach for AHAs if you’re keen to reveal your freshest, healthiest skin ever! But that’s by no means all—they’re also brilliant at improving the appearance of pigmentation, sun damage or uneven texture, as well as treating and combatting acne.

The chemical exfoliation properties of AHAs are a good option for those with sensitive skin – if you are worried about potential irritation or redness, it’s a good idea to try formulas including an amino acid or peptide which will slow penetration into the skin, or choose one of the gentler AHAs over glycolic acid.

If you are blighted with spots or acne on your chest or back, glycolic acid-based body care products can help with more efficient cell turnover and also whisk away rough or scaly patches, leaving skin smoother and more even-toned.

What are BHAs?

A type of acid found in willow bark, willow extract and sweet birch trees, unlike AHAs which are water-soluble, BHAs (beta hydroxy acids) are oil-soluble exfoliators.

Possessing antibacterial and anti-inflammatory properties, they are able to get deeper into the pores and efficiently whisk away the sebum and dead cells responsible for clogging up the skin.

The most commonly used BHA is salicylic acid, a liquid exfoliant which belongs to a class of ingredients called salicylates. This active ingredient helps to rid the skin of dead cells and reduce blemishes while respecting the skin’s natural oils.

Salicylic acid works best at a pH between 3 and 4. Over the counter products normally contain levels between 0.5 per cent and 2 per cent. In-clinic chemical peels are likely to be around 20 to 30 per cent.

What are the skincare benefits of BHAs?

BHAs are your bacteria battlers—they love to work on a deeper level in the pores, making them an excellent choice for treating acne, whiteheads and blackheads.

Sensitive or rosacea-prone skin? The good news is that BHAs are gentle enough for your skin type, and unlike AHAs should not cause sun sensitivity.  

As well as inside the pores, BHAs also work on the skin’s surface. The benefits are numerous—they can help smooth out congested or bumpy skin (such as keratosis pilaris), boost hydration levels, reduce excess oil (ideally at 0.5 to two per cent), work on lines and wrinkles, brighten a dull, uneven tone and even improve dandruff when applied to the scalp.

With their larger molecule size, BHAs are less irritating than other acids, although they can sometimes be drying so those with dry or very dry skin should be cautious. Redness, stinging and irritation is also possible when using certain concentrations.

How do I combine AHAs and BHAs?

If you want to reap the benefits of both AHAs and BHAs in your skincare regime, it is certainly possible to use them both.

Many products now combine the two to good effect, although you do run the risk of skin irritation, redness and flakiness if concentrations are too high.

To use them individually, apply your BHA first to dissolve any oil on the skin, followed by your AHA, which will work in combination to deep clean the pores.

Be careful if you are also planning to use a vitamin C-based product with your acids, as this combo may upset your skin due to excess exfoliation.

Go easy and start with a light formula to prevent irritation—or use your vitamin C in the morning, and your acids in the evening.


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