October 25, 2026

AHA vs PHA: Which Exfoliating Acid Is Right for You?

AHAs and PHAs both loosen the dull, dead cells on the surface of your skin, but they do it at different speeds. AHAs (alpha hydroxy acids) like glycolic and lactic acid are the faster, stronger option for rough, dull, uneven skin. PHAs (polyhydroxy acids) like gluconolactone are the slower, gentler cousins that also pull water into the skin, which is why they are popular with sensitive and dry complexions. If your skin handles acids well, start with an AHA. If it stings at the sight of a toner, start with a PHA.

Below, we break down what each acid is, how they differ, who should pick which, and how to use them without wrecking your moisture barrier.

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TL;DR

  • AHAs (glycolic, lactic, mandelic) exfoliate more actively and are generally preferred for normal to dry skin that is dull or rough. They raise sun sensitivity, so daily sunscreen is a must.
  • PHAs (gluconolactone, galactose, lactobionic acid) have bigger molecules, work on the surface, irritate less and add hydration. They suit sensitive, reactive skin.
  • Neither is the best pick for clogged pores. For oily, acne-prone skin, a BHA (salicylic acid) is the better tool because it can get inside the pore.
  • You can combine PHA with AHA or BHA, but go slowly, and don’t stack everything in one night.
  • Start two to three nights a week, cut back at the first sign of redness or stinging, and wear SPF every morning.

Table of Contents

What exfoliating acids actually do

Your skin sheds dead cells naturally, but the process slows down with age, sun exposure and dryness. Cells hang around, pile up and leave skin looking flat and feeling rough. Chemical exfoliants speed up the shedding by loosening the “glue” between those cells, so you don’t have to scrub anything off.

AHAs do this by disrupting the cellular adhesions in the outer layer of skin, which helps the dead cells release. A 2025 review in the Journal of Drugs in Dermatology describes PHAs as a newer generation that does similar work, with added humectant properties and less irritation.

Think of the top layer of your skin as a brick wall. Physical scrubs knock bricks off from outside. Acids dissolve some of the mortar so bricks lift away on their own. The difference between AHA and PHA is how quickly and how deeply the mortar gets dissolved.

What is an AHA?

Alpha hydroxy acids are carboxylic acids with a hydroxyl group in the alpha position. They were introduced into skincare in the 1970s to encourage cell turnover and collagen synthesis, and they remain some of the most studied cosmetic actives around.

The ones you will see most often:

  1. Glycolic acid: the smallest AHA, so it is generally considered the most active. It is a go-to for texture, dullness and uneven tone.
  2. Lactic acid: often found in gentler formulas and commonly paired with hydrating ingredients.
  3. Mandelic acid: a larger AHA that tends to appear in formulas aimed at sensitive or tone-concerned skin.

What AHAs are good at: smoothing rough texture, brightening a dull complexion, softening the look of fine lines and fading the look of uneven tone over time. Dermatology sources note that AHAs are most helpful for people with dry, rough skin.

What to watch: stinging, redness and dryness, particularly when you start, and sun sensitivity. We’ll get to both below.

What is PHA?

PHA stands for polyhydroxy acid. If you have been wondering “what is PHA acid?”, here is the short version: it is a class of exfoliating acids that works like an AHA but with a bigger molecule and a built-in moisturizing effect. Common PHAs include gluconolactone, galactose and lactobionic acid.

Because PHA molecules are larger than AHA molecules, they penetrate the skin more slowly and act on the surface, which means less irritation. They are also humectants (ingredients that attract and hold water, a bit like a sponge) and show antioxidant activity. And unlike AHAs, they do not increase photosensitivity, according to the same source.

That last point deserves a gentle caveat from us: you should still wear sunscreen every day. PHAs not raising sun sensitivity is a nice perk, not a reason to skip SPF, especially if you pair them with an AHA or retinol.

PHAs have also been studied on photoaged skin. Researchers, including Pearl E. Grimes, have noted that PHAs appear compatible with a range of skin types, including African American, Caucasian and Hispanic/Asian skin, which makes them a versatile option for photoaging concerns.

AHA vs PHA at a glance

AHA PHA
Common examples Glycolic, lactic, mandelic acid Gluconolactone, galactose, lactobionic acid
Molecule size Smaller Larger
Penetration Deeper, faster Slower, surface-level
Exfoliation feel More noticeable, more active Gentle, gradual
Hydration Not a main feature Humectant, draws in water
Irritation risk Higher, especially at the start Lower
Sun sensitivity Increases Does not increase
Best suited to Normal to dry, dull or rough skin Sensitive, reactive or dry skin, including skin with rosacea or eczema

The suitability row comes from this PHA guide, which also says BHAs are better suited to oily, acne-prone skin because they can penetrate pores and dissolve sebum.

Strength, penetration and irritation: how they really differ

It helps to think of this as a dial, not a switch.

Penetration. AHAs are small and travel deeper into the outer skin layers, so they act faster and more visibly. PHAs stay closer to the surface. Slower isn’t worse: it simply means you get a gentler pace of change and fewer surprises.

AHA and PHA compared across four skin effects

Hydration. This is where PHA shines. Exfoliating always carries a bit of a dryness trade-off, because you are removing the top layer. PHAs offset that with their water-binding behavior. Many people describe the feeling as smooth and comfortable rather than tight.

Irritation. Redness, stinging or burning from AHAs is common enough that researchers describe it as generally transient, easing as skin adjusts or when you lower the concentration or frequency. PHAs carry less of that risk, which is why dermatologists such as Dr. Shereene Idriss describe them as an ideal alternative for patients who can’t tolerate traditional AHA or BHA exfoliants.

Results. If you have used both, you will probably notice that AHA results show up faster and look more dramatic, while PHA results are quieter and build gradually. Neither is “better”. It depends on what your skin will tolerate consistently, because the exfoliant you can actually use three times a week beats the strong one you abandon after four days.

Which one should you choose?

Here is a simple way to decide, by skin type and goal.

Normal to dry skin with dullness or rough texture

An AHA is generally the preferred choice here. Glycolic or lactic acid can smooth texture and bring back brightness. If your skin is dry as well as dull, look for an AHA formula that includes hydrating ingredients, and follow with a good moisturizer.

Sensitive, reactive or easily flushed skin

Start with a PHA. If you deal with rosacea or eczema-prone skin, PHAs are described as a better fit than AHAs. Talk to your dermatologist before adding any acid if your skin is actively flaring.

Oily or acne-prone skin

This is where we steer you away from both. AHAs and PHAs improve texture and tone, which can indirectly help with acne-related marks and roughness. But BHAs are generally considered more effective for direct acne treatment because they get into pores and dissolve sebum. Our guide to AHA vs BHA concentrations for oily or dry skin goes deeper, and glycolic vs salicylic acid helps if you are torn between those two.

Aging skin

People often ask whether BHA or AHA is better for aging skin. AHAs have the longer track record here: they were introduced to skincare to promote cell turnover and collagen synthesis. If your skin is on the sensitive side, PHAs offer a gentler route, and the photoaging research on them is encouraging. BHA is mostly an oily-skin tool.

Brand new to acids

If you have never used an exfoliating acid, PHA is the low-risk first step. If you would rather go straight to an AHA, choose a low concentration and build slowly.

A quick decision shortcut

  1. Skin gets red or stings easily? PHA.
  2. Skin is normal to dry, dull and rough, and tolerates actives? AHA.
  3. Oily, with blackheads or breakouts? BHA (with AHA or PHA as a supporting player).
  4. Want results fast and can handle some adjustment? AHA.
  5. Want comfort first and gradual change? PHA.

How to use AHA or PHA safely

Exfoliating acids are some of the easiest actives to overdo. A few ground rules keep things comfortable.

Mind the concentration and pH

For AHAs, the Cosmetic Ingredient Review Expert Panel recommended limiting concentrations to under 10% and keeping product pH at 3.5 or higher. That is a useful yardstick when you are reading a label. If pH is new territory for you, our post on toner pH levels explains why the number matters but isn’t something to obsess over.

Start slow

Begin with two or three evenings a week. Hold there for a few weeks. Only add nights if your skin stays calm. Redness, stinging or burning means pull back: lower the frequency or switch to a lower concentration.

Sunscreen, every morning

The same expert panel advised that AHA products be formulated to avoid enhancing sun sensitivity, and that consumers use daily sun protection. In practice, that means a broad-spectrum sunscreen every morning, including cloudy days, for as long as you use an AHA and for a while after.

Patch test first

Put a small amount on your inner forearm or behind your ear, wait a day, and check for reactions. It takes a minute and saves a lot of regret.

Keep everything else simple

When your skin is adjusting, pause scrubs, harsh cleansers and other strong actives. Irritated skin also reacts to what touches it all day, so it is worth looking at fabrics for sensitive skin, especially pillowcases and collars that rub against your face.

If you have a skin condition, are pregnant or nursing, or are using prescription treatments such as retinoids, ask your dermatologist or doctor before starting acids.

What not to mix with PHA

The good news: PHA is the most mix-friendly of the three. PHAs can be combined with AHAs and BHAs, and if a combination feels too strong, the advice is to take things slowly.

That said, “can” is not “should, all at once”. Our practical rules:

  • Don’t stack multiple exfoliating acids in one night when you are new to them. Alternate nights instead.
  • Be careful pairing with other strong actives such as retinol, especially while your skin is adjusting. Use them on separate evenings.
  • Skip physical scrubs on the same day as acids unless your skin is very resilient.
  • Back off if skin feels tight, shiny, burning or rashy, and give it a few days of just cleanser, moisturizer and sunscreen.

A simple routine for each acid

AHA routine (3 evenings a week to begin)

  1. Cleanse with a gentle, non-stripping cleanser.
  2. Apply your AHA treatment or exfoliant to dry skin, avoiding the eye area.
  3. Follow with a hydrating serum and moisturizer.
  4. In the morning, sunscreen.

PHA routine (every other evening to begin)

  1. Cleanse gently.
  2. Apply your PHA product, then a moisturizer.
  3. Increase to most evenings if your skin loves it.
  4. Sunscreen every morning, because daily SPF is good practice with any exfoliating routine.

Rotation idea if you want both

  • Monday: AHA
  • Tuesday: hydrate only
  • Wednesday: PHA
  • Thursday: hydrate only
  • Friday: AHA
  • Weekend: rest, or PHA if your skin feels great

Adjust to what your skin tells you. Smooth, calm and comfortable is the goal.

Where Cosmedica fits in

Our lineup leans on AHAs, with options for different comfort levels. The 2.5% Glycolic Facial Scrub is a good fit if you want a smoothing glycolic step for rough, dull skin. The 5% Lactic Acid Treatment + Hylasin pairs an AHA with hydration for people who want brightening without feeling stripped. And if you prefer to browse by ingredient, our glycolic acid collection gathers those formulas in one place.

All of our products are cruelty-free and dermatologist-tested, and you can see the full range in our skincare shop. Not sure where to start? Pick one acid, use it on a gentle schedule, and add a moisturizer you love.

Our perspective: gentle and consistent beats strong and sporadic

We talk to a lot of people who have been burned (sometimes literally) by an exfoliant that was too much, too soon. The pattern is almost always the same: a big, exciting first week, a red and tight second week, and then a drawer full of abandoned bottles.

Here is how we think about it. Your skin barrier is the thing doing the real work: keeping water in and irritants out. Acids are a tool for polishing the surface, not a replacement for a healthy barrier. So we always say to choose the acid that your skin will tolerate regularly, add hydration around it, and treat sunscreen as part of the acid, not a separate step.

Our perspective: gentle and consistent beats strong and sporadic — overview diagram

That is why we don’t think AHA and PHA are rivals. AHAs are the confident choice when skin is steady and you want visible smoothing and glow. PHAs are the comforting choice when skin is touchy. Many people end up using both at different times of year, or at different points in their lives. And if your main concern is clogged pores, we would point you to a BHA before either.

If we could give one piece of advice, it would be this: go slower than you think you need to. Skin that is calm, hydrated and protected looks better than skin that is freshly exfoliated and angry.

— Thomas

FAQ

Is PHA better than AHA?

Not across the board. PHA is gentler and more hydrating, with less risk of irritation, so it tends to be better for sensitive or reactive skin. AHA is more active and generally preferred for normal to dry skin that wants faster smoothing and brightening. The better acid is the one your skin tolerates.

Can I use AHA and PHA together?

Yes, they can be combined, but take it slowly. If the pairing feels too strong, use them on alternate nights rather than layering both in one routine. Stop and simplify if you see redness, stinging or peeling.

Are AHA, BHA and PHA good for acne?

AHAs and PHAs improve texture and tone, which can indirectly help with acne-related roughness and marks. BHAs are generally considered more effective for direct acne treatment because they penetrate pores and dissolve sebum. For persistent or painful acne, see a dermatologist.

Do I need sunscreen with PHA?

PHAs do not increase photosensitivity the way AHAs do, but daily sunscreen is still smart. If you use an AHA, retinol or any other exfoliating step, SPF is essential every morning.

How often should I use an exfoliating acid?

Start with two or three times a week and hold there for a few weeks. If skin stays comfortable, you can slowly add nights. If you notice redness, stinging or burning, reduce how often you use it or choose a lower concentration.

Sources