Cosmetics By Nana · 6 min read

AHA, BHA and PHA: chemical exfoliants for home use explained

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Chemical exfoliants sound like a harsh procedure at first, but in everyday use they are usually gentler and more controlled than scrubbing with grains. Instead of mechanical sanding, they dissolve the bonds between dead skin cells so they shed more easily. Behind the abbreviations AHA, BHA and PHA are different acid families with different strengths. Salicylic acid in particular has made a name for itself for blemish-prone skin. In this guide, you’ll learn which acid suits which skin goal, how to dose it correctly and which combinations are better avoided.

What are chemical exfoliants?

A chemical exfoliant removes dead skin flakes not through friction but through an acid that dissolves the “glue” between the uppermost skin cells. The skin constantly renews itself anyway, but over the years and depending on skin type, dead cells linger longer. This makes the complexion look dull, clogs pores and makes unevenness more visible. An acid supports this natural shedding process gently and evenly.

The difference from a mechanical scrub (such as one with grains) lies in control. A scrub acts in spots and can cause micro-injuries if you rub too hard. An acid works across the surface and is easy to dose. For how a classic fruit acid peel works in detail, read the guide on the fruit acid peel and its effects.

The three groups: AHA, BHA and PHA

Chemical exfoliants are roughly divided into three families. What matters is whether the acid is water- or oil-soluble and how large its molecules are.

AHA: fruit acids for glow and smoothness

AHA stands for alpha hydroxy acids. They are water-soluble and work mainly on the skin’s surface. This makes them well suited to bringing dull, dry skin back to a glow and visually smoothing fine lines. The best known include:

• Glycolic acid: the smallest AHA molecule, penetrates deepest and acts most intensely. Very popular for glow, but it can also irritate.
• Lactic acid: slightly larger and milder than glycolic acid, also adds moisture. A good choice for dry skin.
• Mandelic acid: the largest molecule, penetrates slowly and is considered especially gentle. Suitable for sensitive skin that still wants to try an AHA.

BHA: salicylic acid for the pore

BHA stands for beta hydroxy acid, in practice almost always salicylic acid. Its big advantage: it is oil-soluble and can therefore enter the sebum-filled pore and clean it from within. This makes salicylic acid the classic for blemish-prone and oily skin, blackheads and seemingly large pores. It also has a mild anti-inflammatory effect, which is pleasant for skin prone to spots. If you struggle with shine and clogged pores, you’ll find more strategies in the guide oily skin: what really helps.

PHA: the gentle option

PHA stands for polyhydroxy acids (such as gluconolactone or lactobionic acid). Their molecules are even larger than those of AHA, penetrate more slowly and therefore act especially mildly. They also bind moisture. PHA is the entry-level group for sensitive skin, a tendency towards rosacea, or anyone who finds AHA and BHA too strong.

Which acid for which skin goal?

Instead of choosing the strongest acid, go by your goal:

• Dull complexion, fine lines, dry skin: AHA, such as lactic or glycolic acid.
• Blemish-prone, oily skin, blackheads, pores: BHA, meaning salicylic acid.
• Sensitive or reactive skin: PHA or the mild mandelic acid.
• Combination skin: Some combine BHA in the T-zone with AHA on the cheeks.

If even acids feel too intense for you, an enzyme peel as a gentle alternative is worth a look. It uses enzymes instead of acids and is even more tolerable.

Application: concentration, frequency and sun protection

With chemical exfoliants, less is often more. Here’s how to proceed:

1. Start low: For beginners, mild concentrations are enough, around 5 to 8 percent AHA or about 2 percent salicylic acid.
2. Ease in: Begin once or twice a week, ideally in the evening, and only increase if the skin stays calm.
3. Apply: Put it on cleansed, dry skin, leave out the eye and mouth area, then follow with a moisturizer.
4. Sun protection is a must: Acids make the skin more light-sensitive. During the day, a high-SPF sunscreen is essential, otherwise you risk pigment spots.

A slight tingling right after applying is normal; lasting burning, redness or flaking is a sign that you used it too often or too high a dose. Leave out the mouth area consistently, as the thin skin of the lips reacts sensitively to acids; for chapped lips the guide on what helps against dry, cracked lips is useful.

What you should NOT combine

Acids work, but they also stress the skin barrier. Avoid these mistakes:

• Not with retinol in the same application: Both speed up cell renewal. Together they risk over-irritation. Put them on different evenings.
• Don’t stack high-dose vitamin C on top: In a routine full of actives, the skin quickly gets overwhelmed. Separate strong actives in time.
• Not with a mechanical scrub: If you already use an acid, you don’t also need a scrub. That’s double exfoliation and irritates.
• Not daily if the skin feels tight: Breaks are part of care. An intact barrier matters more than fast results.

Similar principles apply to the body. The guide making body scrub yourself shows gentle recipes, though more mechanical there and for the more robust skin of the body.

Frequently asked questions (FAQ)

What is the difference between AHA and BHA? AHA are water-soluble and work on the skin’s surface, ideal for glow and fine lines. BHA (salicylic acid) is oil-soluble, penetrates into the pore and suits blemish-prone, oily skin and blackheads.

How often should I use a chemical exfoliant? Start once or twice a week and increase only slowly. Most skin needs no more than two or three times a week. Watch how your skin reacts and give it breaks.

Do I really need sunscreen after an acid exfoliant? Yes, absolutely. Acids make the skin more light-sensitive. Without daily sun protection you risk irritation and pigment spots that undo the result.

Is salicylic acid suitable for every skin type? Salicylic acid shows its strength mainly with oily and blemish-prone skin. For very dry or sensitive skin, mild AHA or PHA are often the better choice because they also bind moisture.

Can I use AHA, BHA and PHA together? Some products already combine them in a balanced way. You shouldn’t stack them yourself, as the skin easily gets over-irritated. Better to choose one acid that fits your goal and stick with it.

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