Salicylic or glycolic acid: which one for your skin?

It depends on what you want it to do. Salicylic acid, the most common BHA in cosmetics [3], dissolves in oil, so it mixes with the oils inside hair follicles [6]. The American Academy of Dermatology (AAD) says it opens clogged pores [4]. Glycolic acid, one of the two most common AHAs [2], is on the AAD’s list for fading dark spots [5]. Both are exfoliants [1].

How they differ

Both are chemical exfoliants. The AAD says they dissolve dead skin cells [1]. The difference is where they reach. Salicylic acid is lipid soluble, in contrast with AHAs such as glycolic acid [6]. A review of salicylic acid peels says it concentrates in the oil glands around hair follicles, which makes it useful for acne-prone skin [6].

Picking by skin type

• Oily or breakout-prone skin. The AAD says salicylic, glycolic and lactic acid can help reduce oiliness, but may be too harsh for your skin [9]. Salicylic acid is the one the AAD links to clogged pores [4].
• Dark spots or uneven tone. The AAD lists glycolic acid among ingredients that can fade dark spots [5]. It also warns that aggressive exfoliation on darker skin tones can lead to more dark spots [1].
• Dry or sensitive skin. The AAD suggests a mild chemical exfoliant over a scrub, since scrubs may be too irritating [1]. For sensitive skin, it suggests skipping moisturizers with alcohol, AHA or fragrance [10].

If you are not sure, start gently. The AAD says the more aggressive the exfoliation, the less often it needs to be done [1].

Sun protection with each

Glycolic acid needs daily sunscreen. The FDA’s suggested label for AHA products says to use sunscreen, wear protective clothing and limit sun exposure while using the product and for a week afterward [2]. In one study, 10% glycolic acid increased the skin’s sensitivity to simulated sunlight, while 2% salicylic acid did not [8]. The FDA still advises sun protection with BHA products [3].

Can you use both?

Corneo’s rules do not keep salicylic and glycolic acid apart. That does not mean more is better. The AAD warns that over-exfoliating can leave skin red and irritated [1]. The FDA suggests testing a BHA product on a small area first, and not using it more often than the label says [3]. Acne product labels with salicylic acid warn that irritation and dryness are more likely with another acne product at the same time [7].

A cautious approach is one acid at a time. Add the second only once your skin is settled on the first.

In Corneo, neither acid goes on a retinol night. See retinol with AHA or BHA for how Corneo keeps them apart.

What Corneo does

Corneo checks salicylic and glycolic acid against the rest of your shelf. Its rules keep both off retinoid nights, ask for sunscreen when either is in your routine, and flag more than 2 exfoliating nights a week if you said your skin is sensitive. Check this pair or audit your whole shelf.

FAQ

Is salicylic acid gentler than glycolic acid?

The sources here do not settle it. The FDA says it has been claimed that BHAs work without the occasional irritation of AHAs [3]. That is a claim the FDA reports, not a finding. The AAD says either may be too harsh for some skin [9].

What strength should I look for?

Over-the-counter acne products use salicylic acid at 0.5 to 2 percent [7]. For glycolic acid, an expert panel found cosmetics safe at 10 percent or less, with a pH of 3.5 or higher [2].

How often should I use one?

The AAD says it depends on your skin type and exfoliation method [1]. Salicylic acne labels say to start with 1 application a day, and to cut back to every other day if dryness or peeling bothers you [7].