Glycolic acid vs salicylic acid: which to use?

Neither one is better. Glycolic acid is an alpha hydroxy acid and dissolves in water, so it works across the surface. Salicylic acid is a beta hydroxy acid and dissolves in oil, so it gets inside the pore. The two also stop being interchangeable in pregnancy, and that part is usually missing.

By The Truva teamPublished

Answers for 6 life stages13 sources, all linked8 min read

What is the difference between glycolic acid and salicylic acid?

Glycolic acid and salicylic acid are both chemical exfoliants, and the one difference that matters is what they dissolve in. Glycolic acid is an alpha hydroxy acid and dissolves in water, so it works across the surface of the skin. Salicylic acid is a beta hydroxy acid and dissolves in oil, so it gets down inside a pore. Almost everything else ever written about the pair follows from that.

The chemistry is one sentence each. StatPearls, on the NIH’s own bookshelf, calls glycolic acid an alpha hydroxy acid (AHA) whose hydroxyl group sits at the alpha position, and salicylic acid a beta hydroxy acid that features a hydroxyl group connected to the second carbon. Moving one group one carbon along changes what the molecule mixes with, and the same page draws the consequence: salicylic acid boasts higher lipophilicity than glycolic acid, which is why it can permeate acne lesions and oily skin.

Both acids belong to one family of jobs. The American Academy of Dermatology calls it a keratolytic, and names glycolic acid and salicylic acid on the same short list of ingredients that qualify. StatPearls says what one does: keratinolytics disrupt bonds between keratinocytes, forcing them to shed. Both acids do that. Only one can do it inside a follicle.

Where glycolic acid and salicylic acid each go in the skinTwo cross sections through the same skin, one above the other. Each shows a shallow surface layer packed with dead skin cells, deeper skin below it, and one hair follicle running down from the opening. In the top panel, labelled glycolic acid, an alpha hydroxy acid, the acid is drawn as a row of dots spread evenly across the surface from one side to the other, including directly over the follicle opening, and three dead cells are lifting away above the surface. None of the dots go into the follicle. In the bottom panel, labelled salicylic acid, a beta hydroxy acid, the follicle is filled with oil and the acid is drawn as a column of dots running from above the surface down through the opening and along the inside of the follicle, with a few dots also left on the surface. The difference between the two panels is the direction the dots travel: sideways across the top in one, downwards into the pore in the other.Glycolic acid, an alpha hydroxy acidIt works across the surfaceGlycolic acid is water soluble. It loosensthe bonds holding dead cells onto the toplayer, and those cells shed.It does not go down the poreOil inside a follicle repels it, so ablackhead is not the job this acid isbest at.Salicylic acid, a beta hydroxy acidIt follows the oil downSalicylic acid is oil soluble. It mixes withthe sebum filling a follicle and works onthe plug from the inside.It exfoliates the surface tooBoth acids loosen dead cells at the top.Only one of them gets past the oil atthe opening.
The same skin, treated with each acid. Glycolic acid dissolves in water, so it works across the surface layer and passes over a follicle opening. Salicylic acid dissolves in oil, so it mixes with the sebum inside a follicle and works on the plug from the inside. That one difference is why the two acids suit different problems.This diagram is wider than the screen. Drag it sideways to see the rest.

What does glycolic acid actually do?

Glycolic acid sheds the top layer of the skin, so what people notice from it is texture, tone and dark spots rather than fewer spots. The FDA states it plainly: products containing an AHA cause exfoliation, or shedding of the surface skin.

Dark spots are the clearest use. Glycolic acid is one of five ingredients the AAD names for fading them without a prescription, and the page says these ingredients can fade existing dark spots. At professional strengths it becomes a procedure: StatPearls puts 30% to 50% glycolic acid in the light peel band, aimed at melasma, wrinkles, photodamage and acne scars.

Glycolic acid carries a cost too. The FDA’s own studies found that applying AHAs to the skin results in increased UV sensitivity: after four weeks, sensitivity to reddening from UV rose by 18 per cent and sensitivity to UV induced cellular damage roughly doubled, reversing within a week of stopping. The label the FDA recommends tells you to use a sunscreen, wear protective clothing, and limit sun exposure while using this product and for a week afterwards. The Cosmetic Ingredient Review panel calls glycolic acid safe for consumers at 10 per cent or less, at pH 3.5 or greater, with sun protection in the formula or the directions.

Glycolic acid changes how skin looks, and it also makes skin more vulnerable to the thing that caused most of what you are treating. Running it without daily sunscreen is close to pointless.

What does salicylic acid actually do?

Salicylic acid clears the inside of a blocked follicle, which is why it sits on the acne aisle rather than the anti ageing one. The AAD’s wording is short enough to quote whole: because it unclogs pores and exfoliates the skin, salicylic acid works best on whiteheads and blackheads.

The reason salicylic acid can is the solubility. A blackhead is a follicle packed with sebum and dead cells, and a water soluble acid arriving at the opening has nothing there to dissolve into. Salicylic acid does, which is why StatPearls names lipophilicity as the property letting it effectively permeate acne lesions and oily skin. The second half of that phrase is the part people skip: an acid that mixes with oil keeps working on skin that makes a lot of it.

Sun is on the salicylic acid regulator page too, which stops this being a clean win. The FDA calls it the BHA most commonly used in cosmetics and quotes the Cosmetic Ingredient Review panel calling it safe as used when formulated to avoid irritation and when formulated to avoid increased sun sensitivity. Sunscreen is not a glycolic acid tax. It is the price of exfoliating at all.

Which acid should you use for your skin?

Choosing between glycolic acid and salicylic acid is a question about your complaint rather than about which is stronger, and it has four answers.

If your complaint is texture, tone or dark spots, use glycolic acid

Glycolic acid is the answer to a surface problem, and dark spots, uneven tone and roughness all are. Wear the sunscreen, because of the 18 per cent above.

If your complaint is blackheads, whiteheads or oily skin, use salicylic acid

Salicylic acid is the answer to a problem that lives inside the pore, which blackheads and whiteheads both do. That is the AAD’s own allocation, and oily skin belongs here for the same reason. The single inflamed spot that has already arrived is a different question, and our post on getting rid of a pimple overnight covers what one evening can and cannot do about it.

If your complaint is rough bumps on your arms, either will do

Keratosis pilaris is the one complaint where the choice barely matters, because the AAD names both acids in the same keratolytic list for it. Our keratosis pilaris post sets out the rest of that routine.

If your complaint is both, nobody has published a schedule

Using both acids is common advice with no published protocol behind it, so this post will not invent one. What is published is the warning that covers either: applying a keratolytic too often or in too great a quantity, the AAD says, can cause raw, irritated skin. Two exfoliants at once is the fastest route there. What goes on skin an acid has already left tender is the other half of that question, and our post on what niacinamide does for skin takes it.

Does the answer change if you are pregnant or breastfeeding?

Pregnancy is where glycolic acid and salicylic acid stop being interchangeable. Both sit on the same list of over the counter ingredients that ACOG says can be used during pregnancy, with no concentration and no area limit on either. One of them then picks up a limit from somebody else, which is why only one of the two appears in our catalogue at all. That catalogue publishes the flagged ingredients and nothing else: salicylic acid is in it, at Caution Advised for pregnancy and for trying to conceive, and glycolic acid is not in it.

Glycolic acid and salicylic acid against six profilesA grid with two columns and six rows. The columns are glycolic acid, an AHA, and salicylic acid, a BHA. The rows are pregnancy, breastfeeding, postpartum, trying to conceive, PCOS and general use. In pregnancy, glycolic acid is safe to use because ACOG lists it and the AAD suggests it, while salicylic acid is caution advised because ACOG lists it but the AAD limits it above 2 per cent. While breastfeeding, both acids are caution advised, because LactMed says each is safe with a condition attached. Postpartum, both are safe to use with no life stage limit. When trying to conceive, both have no published rule, because no body has written one either way. With PCOS, both are safe to use because PCOS adds no limit. For general use, both are safe to use because the AAD names both. Pregnancy is the only row in which the two acids differ from each other.Glycolic acidan AHASalicylic acida BHAPregnancySafe to UseACOG lists it andthe AAD suggests itCaution AdvisedACOG lists it, theAAD limits it above 2%BreastfeedingCaution AdvisedLactMed says safe,with a conditionCaution AdvisedLactMed says safe,with a conditionPostpartumSafe to UseNo life stage limitSafe to UseNo life stage limitTrying to ConceiveNo published ruleNo body has writtenone either wayNo published ruleNo body has writtenone either wayPCOSSafe to UsePCOS adds no limitSafe to UsePCOS adds no limitGeneral UseSafe to UseThe AAD names bothSafe to UseThe AAD names both
Glycolic acid and salicylic acid against the six profiles Truva answers for, with the body behind each cell named inside it. Every cell is discussed below with its source linked. No published rule is not a verdict: it marks where nobody has written anything either way, which is silence rather than a clearance.This diagram is wider than the screen. Drag it sideways to see the rest.

If you are pregnant

Pregnancy is the row where the two acids separate. ACOG’s list runs to topical benzoyl peroxide, azelaic acid, topical salicylic acid and glycolic acid, with the instruction to ask your obstetrician about anything not on it. The American Academy of Dermatology does differentiate them: its pregnancy skin care page carries a list of ingredients to use sparingly and discuss with a dermatologist, and the first item on it is salicylic acid at high doses (greater than 2%). Glycolic acid is on neither that list nor the page’s avoid list; it appears in the routine the page recommends: a product containing vitamin C in the morning, and one containing glycolic acid in the evening.

The AAD’s acne page is gentler and says the same. Salicylic acid is generally considered safe when used for a limited time, so talk to your obstetrician or dermatologist first. Glycolic acid is not on that page at all. A peel of either acid gets a firmer answer: StatPearls lists pregnancy or breastfeeding among the precautions specific to medium and deep chemical peels. The absorption numbers do not settle it either. A review in Canadian Family Physician puts salicylic acid at anything from undetectable up to 25 per cent through normal skin, with levels might be higher when applied to damaged skin, and glycolic acid at up to 27 per cent, then concludes that neither is a concern at cosmetic use and that neither has been studied in human pregnancy. The AAD’s limit is a judgement, not a finding. Our post on whether salicylic acid is safe during pregnancy follows that one ingredient the rest of the way: what strength your product actually carries, why the aspirin comparison keeps coming up, and what changes while breastfeeding.

If you are breastfeeding

Breastfeeding puts the two acids back together with the same condition on each. The NIH’s Drugs and Lactation Database considers salicylic acid safe to use during breastfeeding and says the same of glycolic acid, in both cases because neither is likely to be appreciably absorbed. Both attach the identical instruction: avoid areas that might contact the infant’s skin or be ingested. Both also open by saying no clinical information is available. A verdict with a condition on it is a caution.

If you are trying to conceive

Trying to conceive is the row where both acids agree, and what they agree on is that nobody has written anything. Every instruction above is about pregnancy or breastfeeding, and there is a window in which somebody is pregnant before they know. Marking either acid Safe to Use would report a clearance no body has issued; Caution Advised would report a concern no body has raised. The pregnancy rules are the ones to read early.

If you are postpartum and not breastfeeding

Postpartum without breastfeeding returns you to the general answer, though the complaint often changes here. ACOG says dark spots and melasma usually fade on their own after you give birth, but that some women have dark patches lasting for years. That is a glycolic acid problem, not a salicylic acid one.

If you have PCOS

PCOS does not change what you may put on your skin, and it does change which acid is more likely to be yours. NICHD lists among the symptoms of PCOS persistent acne that does not respond well to common treatments, and separately lists oily skin. Both point at the oil soluble acid, and the second half of that phrase is a warning: acne that resists common treatments will resist an acid too.

This split is what Truva was built to make. The comparison pages set out why a scanner that never asks your situation cannot make it.

When should an acid go to a dermatologist instead?

An acid that has left your skin raw, stinging or peeling is the signal to stop, and the AAD says to pause for a few days rather than push through. Acne that scars, and dark patches that have not shifted after months of daily sunscreen, belong with a professional rather than with a stronger product. If you are pregnant or breastfeeding, take the ingredient list to your obstetrician or midwife: the only concentration limit anybody has published for these two acids is the AAD’s 2 per cent on salicylic acid.

Key takeaways

Where this came from

Every health claim on this page links to the body that published it. Nothing here comes from another blog.

Show all 13 sources
  • StatPearls, NIH National Library of MedicineChemical Peels for Skin ResurfacingThe chemistry that separates the two acids: glycolic acid is an alpha hydroxy acid, salicylic acid a beta hydroxy acid, and salicylic acid's higher lipophilicity is what lets it permeate acne lesions and oily skin.
  • American Academy of DermatologyKeratosis pilaris: Self-careThat glycolic acid and salicylic acid appear on the same list of keratolytic ingredients, and the warning that applying one too often can cause raw, irritated skin.
  • U.S. Food and Drug AdministrationAlpha Hydroxy AcidsThat AHAs cause exfoliation and increase UV sensitivity, measured at an 18 per cent rise in reddening sensitivity after four weeks, reversing within a week of stopping.
  • U.S. Food and Drug AdministrationBeta Hydroxy AcidsThat salicylic acid is the BHA most commonly used in cosmetics, and the Cosmetic Ingredient Review conclusion that it is safe as used when formulated to avoid irritation.
  • American Academy of DermatologyAdult acne treatment dermatologists recommendWhat salicylic acid is for: because it unclogs pores and exfoliates, it works best on whiteheads and blackheads.
  • American Academy of DermatologyHow to fade dark spots in darker skin tonesThat glycolic acid is one of five over the counter ingredients the AAD names for fading dark spots.
  • American College of Obstetricians and GynecologistsSkin Conditions During PregnancyThat topical salicylic acid and glycolic acid both appear on the list of over the counter ingredients that can be used during pregnancy, with no concentration or area limit on either.
  • American Academy of DermatologyDermatologist-approved pregnancy skin careThe distinction ACOG does not draw: salicylic acid above 2 per cent heads the list of ingredients to use sparingly and discuss with a dermatologist, while glycolic acid is on neither that list nor the avoid list.
  • American Academy of DermatologyIs any acne treatment safe to use during pregnancy?That salicylic acid is generally considered safe when used for a limited time, with the instruction to talk to your obstetrician or dermatologist first.
  • Canadian Family Physician, via PubMed CentralSafety of skin care products during pregnancyThe absorption figures behind the disagreement: salicylic acid undetectable up to 25 per cent through normal skin, glycolic acid up to 27 per cent, and that neither has been studied in human pregnancy.
  • Drugs and Lactation Database (LactMed), NIHSalicylic AcidTopical salicylic acid while breastfeeding: considered safe to use, avoiding areas that might touch the infant's skin.
  • Drugs and Lactation Database (LactMed), NIHGlycolic AcidTopical glycolic acid while breastfeeding: considered safe to use, on the identical condition about where it is applied.
  • Eunice Kennedy Shriver National Institute of Child Health and Human DevelopmentPolycystic Ovary Syndrome (PCOS)That persistent acne and oily skin are both listed symptoms of PCOS, which is what points a PCOS reader at the oil soluble acid, and what the PCOS post is built on.

Every link above was fetched and confirmed to resolve on .

Truva summarises published guidance from bodies including ACOG, the FDA, the EU SCCS and the Cosmetic Ingredient Review. It has no access to your medical history and it is not a substitute for your doctor, dermatologist or midwife. This post was written by the Truva team from the sources listed above. It has not been reviewed by a clinician, and nothing in it is a diagnosis or a prescription. If you are pregnant, breastfeeding or being treated for PCOS, take the ingredient list to the person looking after you.

The label in your hand, read against your situation.

Truva scans a product and answers for the profile you set: pregnancy, breastfeeding, postpartum, trying to conceive, PCOS, or general use. Every flag names the body it came from, so you can take it to a doctor or midwife rather than take it on trust.

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