Salicylic acid

Acid0.5–2%

An oil-loving exfoliating acid that helps pores look clearer and oily, blemish-prone skin look smoother.

What it is

Salicylic acid is a beta hydroxy acid that mixes with oil, so it works within pores as well as on the surface. It helps clear the build-up of oil and dull surface skin that makes pores look congested. It suits oily and blemish-prone skin and is common in cleansers, toners and spot products.

Good for

BlackheadsVisible poresOily skinBlemish-prone skinFlaky scalp

How it works

Salicylic acid is thought to loosen the bonds between surface skin cells so they shed more evenly, including along the pore lining. It works best in an acidic formula, where more of it is in its active, un-ionised form.

Ratings

Evidence

4/5

Good trial data for the look of blackheads and texture.

Gentleness

3/5

Can dry or sting, especially when layered with other acids.

Formulation difficulty

3/5

Poorly soluble in water and needs glycols or alcohol to dissolve.

Cost

1/5

Inexpensive commodity raw material.

Popularity

5/5

The most-searched skincare ingredient in 2024 Google search data.

Pairs and cautions

Pairs well with

In a routine. Pairing in one formula depends on matching pH windows.

Take care with

Retinoids or strong AHAs in the same productAdds irritation
High-pH basesMostly ionised as salicylate; check exfoliation in the finished formula

Formulations it suits

Gel and foaming cleanser Toner, essence and face mist Serum Gel Clay mask Body wash Lotion ShampooScalp scrub

Packaging

Regional considerations

Australia	Schedule 3 only above 40% for skin use. A cosmetic anti-acne product may only claim to control or prevent acne through cleansing, moisturising, exfoliating or drying the skin, and must contain no Schedule 2, 3, 4 or 8 substance.
European Union	As an active (not a preservative), capped at 2% in most products, 3% in rinse-off hair care and 0.5% in body lotion, eye shadow, mascara, eyeliner, lipstick and roll-on deodorant; banned in inhalable sprays, oral products and products for children under 3. The UK applies the same limits.
United States	Any acne claim makes it an OTC drug, allowed at 0.5–2% with a Drug Facts label; without acne claims it can be sold as a cosmetic exfoliant.
Japan	Ordinary cosmetics are limited to 0.2% under the Standards for Cosmetics; acne products at higher levels must be approved as quasi-drugs.

In the lab

Specifications

Typical use level

0.5–2%0525%

pH window

pH 3–42 acid7 neutral10 alkaline

Solubility

Alcohol-solubleOil-soluble

Sensitive to

Metal ionsHigh pH

0.5–2% in leave-on blemish serums, toners and cleansers; rinse-off shampoos and scalp scrubs use up to 3%.

INCI	Salicylic Acid
Also known as	BHA, Beta hydroxy acid
Origin	synthetic

Lab notes

Solubility and phase

Pre-dissolve in ethanol, propanediol, butylene glycol or a compatible ester, since only about 0.2% dissolves in water.

Stability

Run freeze–thaw cycles, since it can recrystallise in the cold or if solvent evaporates. Include a chelator to stop iron discolouring it.

Regulatory, Australia

Listed on the AIIC, and Schedule 3 in the Poisons Standard applies only above 40% for dermal use. Cosmetic anti-acne products must contain no Schedule 2, 3, 4 or 8 substances and may only claim to control or prevent acne through cleansing, moisturising, exfoliating or drying the skin.

Claims to take care with

'Helps unclog pores' and 'helps prevent blemishes by exfoliating' are cosmetic, while 'treats', 'stops' or 'heals' acne makes it a therapeutic good. Willow bark extract contains salicin rather than salicylic acid, so avoid calling it 'natural BHA'.