Which acid is right for me?

Glycolic acid

Type

Water-soluble · surface

Strength

Can be very strong

How to start. Start once or twice a week, at night, and build toward nightly only if your skin stays calm (Cleveland Clinic).

Watch for. AHAs raise sun sensitivity: in an FDA-cited study skin reddened 18% more easily under UV after 4 weeks. Wear sunscreen while you use it and for a week after.

Cleveland Clinic: facial acids · Cleveland Clinic: glycolic acid · FDA: AHAs

Lactic acid

Type

Water-soluble · surface

Strength

The gentler AHA

How to start. Same AHA routine as glycolic — a couple of nights a week to start — but it is the milder one Cleveland Clinic points sensitive skin to.

Watch for. Still an AHA, so it raises sun sensitivity: sunscreen while you use it and for a week after (FDA).

Cleveland Clinic: facial acids · FDA: AHAs

Salicylic acid

Type

Oil-soluble · into pores

Strength

Used twice a day by most

How to start. A thin layer once a day on clean skin (FDA acne rule). Add a second time only if you need it, and cut back if your skin gets dry.

Watch for. The FDA advises daily sun protection when sun sensitivity is expected, and a 3-day test on one or two small spots before first use.

FDA acne rule · FDA: BHAs · FDA: allergic reactions

Azelaic acid

Type

Not an AHA or BHA

Strength

One of the gentler actives

How to start. DermNet’s gentle start: once a day on clean, dry skin, then twice a day if your skin tolerates it. The prescription labels say twice a day.

Watch for. Both labels note rare lightening of the skin, so on darker skin watch for lighter patches.

DermNet: azelaic acid · Azelaic 15% gel label · Azelaic 20% cream label

Clogged pores & blackheads: salicylic acid

A BHA is oil-soluble, so it gets deeper into pores than AHAs do and dissolves the sebum that blocks them (Cleveland Clinic). The AAD says salicylic acid opens clogged pores and exfoliates; DermNet says it helps break down blackheads and whiteheads.

Sensitive? Keep it to once a day; if it dries you out, the AAD says use a plain cleanser in the morning and the salicylic one at night.

Cleveland Clinic: facial acids · AAD: acne treatment · DermNet: salicylic acid · AAD: large pores

Rough or dull texture: glycolic acid

AHAs are water-soluble and work on the surface. Cleveland Clinic says glycolic acid — the smallest AHA, so it reaches a little deeper — smooths the surface and helps with discoloration and fine lines, but can be very strong.

Sensitive skin: lactic acid. On reactive skin, Cleveland Clinic points to lactic acid instead: it is one of the gentler AHAs, the one it suggests for sensitive skin, and still works on surface texture.

The AAD says dry, sensitive or acne-prone skin may prefer a mild exfoliator, and that over-exfoliating leaves skin red and irritated.

Cleveland Clinic: facial acids · Cleveland Clinic: glycolic acid · AAD: exfoliating

Dark spots & marks: glycolic acid

The AAD lists glycolic acid among ingredients that fade dark spots, and Cleveland Clinic says it can lighten spots from mild sun damage or acne. Expect months — a spot a few shades darker usually fades in 6 to 12 months (AAD).

Sensitive skin: azelaic acid. Azelaic acid is the gentler route to the same goal: DermNet lists it for post-acne marks and melasma, the AAD puts it among dark-spot faders, and it is one of the gentler actives.

The AAD says apply sunscreen first and stop any product that burns or stings — new sun exposure is what darkens a spot again.

AAD: dark spots · Cleveland Clinic: glycolic acid · DermNet: azelaic acid

Redness & rosacea bumps: azelaic acid

Azelaic acid is the one with a rosacea label: the 15% gel is FDA-labeled for the bumps and pimples of rosacea, twice a day, and the AAD lists it as a rosacea treatment. It calms inflammation and the redness-linked bumps.

For reactive or rosacea-prone skin the AAD actually lists glycolic and lactic acid among things to avoid — another reason to reach for azelaic here, not an AHA or BHA.

Azelaic 15% gel label · AAD: rosacea · DermNet: azelaic acid · AAD: rosacea skin care