If you have been interested in skincare for a little while, chances are you already have a pretty decent idea of how AHA, BHA, or PHA acids can help your skin. In other words, you know what chemical exfoliation is, and why so many women swear by it.
A lot of us love exfoliation because it can:
- ‘Lift off’ dead skin cells, helping renew the surface of your skin
- Dissolve oil and deal with the buildup that settles in your pores
- Support hydration
- Make your skin look brighter pretty quickly (and yes, it often looks a bit fresher and more youthful)
AHA and BHA acids are popular for a reason. We have finally learned which one tends to suit which skin type and why. And if you are not 100% sure, no worries. I will recap the basics below.
And more and more, there is another player in the mix: PHA acids.
PHA: the gentle friend in your routine
PHA (Polyhydroxy Acids) are water-soluble, so they are often grouped with AHAs. The main difference is that PHA molecules are a bit larger, which means they do not penetrate as deeply. They mostly work on the surface, so they are gentler and more skin-friendly.
That is why PHA can be a great option even if you have sensitive skin, including rosacea, or if your skin just does not tolerate AHA or BHA well.
What PHA can do for your skin:
- It is suitable for sensitive skin because it is less irritating.
- It helps your skin look fresher because it helps reduce moisture loss, so your skin stays more hydrated.
- Your skin can feel healthier, because many PHA formulas also bring antioxidant and anti-inflammatory benefits.
- Your skin can look smoother and more ‘youthful’, because PHA may help slow down glycation, a process that damages collagen and elastin and is linked to a high intake of sugars (natural or heavily processed).
What is the difference between AHA, BHA, and PHA?
AHA (Alpha Hydroxy Acids)
The most common AHAs are glycolic acid, lactic acid, and mandelic acid. Each one has its own ‘strength,’ but the principle is similar. They help remove dead cells (or speed up cell turnover), so fresher cells can come to the surface.
AHAs can be quite active—of course, it depends on the concentration—so they’re often used 2–3 times a week.
BHA (Beta Hydroxy Acid)
In skincare, BHA is mainly salicylic acid. A simple way to picture it is that it helps clear out the pore where oil has settled. It dissolves the oil, and then helps your pores get rid of that loosened ‘stuff.’
PHA (Polyhydroxy Acid)
PHA works on the cell turnover principle too (like AHA), but with much lower risk of irritation, so it can often be used daily. PHA also plays nicely with other actives and antioxidants—even retinoids. And if you have acne-prone skin, it can be used alongside salicylic acid.
A quick overview of exfoliating acids
AHA / Alpha Hydroxy Acids
- Work mostly on the skin’s surface by loosening the ‘glue’ that holds dead cells in place (often mixed with oil on the surface).
- Water-soluble.
- Often better for dry skin or pigmentation spots.
- Can support an anti-ageing routine and help with hydration to a degree.
- Can help other skincare absorb a little more easily.
Types of AHA
Glycolic acid
- Very effective, with small molecules that can penetrate deeper.
- Improves skin texture and helps brighten.
- Can help reduce excess oil to some extent.
- Helps with pigmentation spots.
- Lowers skin pH, which can be helpful in acne routines.
Lactic acid
- Smooths skin, supports cell turnover, improves elasticity.
- A gentler AHA option.
- Great for dry and sensitive skin, also suitable for mature skin.
- Has strong hydrating properties—attracts and binds water in the skin.
Malic acid
- Softens and moisturises the skin.
- May help stimulate collagen production. Often a good fit for mature, tired-looking skin.
- Smaller molecules can penetrate deeper.
Mandelic acid
- Very gentle, with larger molecules, so it does not go as deep.
- Especially good for sensitive skin.
- Also suitable for skin with pigmentation spots.
Citric acid
- Used mainly for brightening and helping with pigmentation.
- Has mild astringent effects, which can help minimise the look of pores.
Tartaric acid
- Has antioxidant and anti-inflammatory properties.
BHA / Beta Hydroxy Acid
BHA acids are, for now, represented mainly by salicylic acid.
Salicylic acid:
- Oil-soluble, which means it can get into pores and start dissolving oily buildup.
- Helps prevent blackheads that can later turn into inflamed breakouts.
- Often a good match for oily or acne-prone skin, and also skin that tends to get redness.
PHA / Polyhydroxy Acid
- Larger molecules, so they work mainly on the surface.
- Gentle, even for sensitive skin.
- Noticeable hydrating properties + antioxidant and anti-ageing benefits,
- Suitable for all skin types.
Types of PHA
Lactobionic acid:
- One of the most used PHA acids, often called a “next generation” acid.
- Helps bind water and reduce water loss; antioxidant and anti-ageing benefits. Supports skin regeneration.
- Can be used without problems even during the sunniest months of the year.
- Suitable for all skin types, especially skin with rosacea.
Gluconic acid:
- Gentle and well-tolerated; antioxidant, hydrating, anti-inflammatory, and anti-ageing properties.
- Suitable for all skin types, especially skin with pigmentation spots.
