Lactic, Glycolic or Salicylic Acid? Choosing an Acid for Body Bumps

Acids have largely replaced gritty scrubs in dermatologists’ advice for bumpy body skin, for good reason. They loosen the bonds that hold dead cells together instead of tearing at the surface. But “use an acid” isn’t specific enough. Lactic, glycolic and salicylic acid behave differently on skin, and the right one depends on what is causing your bumps.

How exfoliating acids smooth bumps

Most rough body bumps involve a buildup of keratin or dead cells around hair follicles. In keratosis pilaris, keratin plugs the follicle opening. In strawberry legs, pores and follicles fill with oil and debris. Acids help in two broad ways.

Alpha hydroxy acids (AHAs), including lactic and glycolic acid, are water-soluble. They loosen the cohesion between surface skin cells so they shed more evenly (Moghimipour, 2012). Beta hydroxy acid (BHA), meaning salicylic acid, is lipid-soluble. A review in Clinical, Cosmetic and Investigational Dermatology explains that it mixes with the oils inside hair follicles, which lets it concentrate in the pore itself (Arif, 2015).

The American Academy of Dermatology (AAD) lists alpha hydroxy acid, glycolic acid, lactic acid, salicylic acid and urea among the exfoliating ingredients dermatologists use for KP. (Urea isn’t an acid, but it often sits alongside them; we cover it separately in urea for keratosis pilaris.)

Lactic acid for keratosis pilaris

Lactic acid has the most direct evidence for KP. In a randomized, double-blind trial, 50 people applied 10% lactic acid cream to one side of the body and 5% salicylic acid cream to the other, twice daily for 12 weeks. Lactic acid reduced lesions by an average of 66%, salicylic acid by 52%, and the difference was statistically significant (Kootiratrakarn et al., 2015). Both improved skin hydration. The only side effect was mild burning or itching without visible reaction, reported more often with lactic acid.

Part of lactic acid’s appeal is that it does double duty. A 2024 review notes that lactic acid is a natural part of the skin’s own moisturizing factor, acts as a humectant, and stimulates ceramide production in the outer skin layer (Feng et al., 2024). Its molecule is also larger than glycolic acid’s (about 90 versus 76 daltons), so it penetrates more slowly. For dry, rough KP, that combination of exfoliation and hydration fits the problem well.

Glycolic acid: the strongest penetrator

Glycolic acid is the smallest AHA (Moghimipour, 2012), which lets it penetrate efficiently. That makes it effective on thickened, rough texture, and also more likely to cause stinging or burning right after application, a known side effect of AHAs.

Glycolic acid has a particular role in razor bumps. A review of treatment options for pseudofolliculitis barbae reports that daily glycolic acid has been found useful, and that glycolic acid peels appear to reduce the curvature of the hair, which lowers the chance that it grows back into the skin (Ogunbiyi, 2019). The same review notes that this kind of bump also appears on the legs, pubic area and underarms of women who shave those areas.

Like all AHAs, glycolic acid raises sun sensitivity. FDA-sponsored research found that after four weeks of AHA use, volunteers’ sensitivity to UV-induced reddening rose by 18% (FDA).

Salicylic acid: the pore specialist

Because it is oil-soluble, salicylic acid works where clogged follicles start. Arif’s review describes it as acting mainly by loosening the connections between skin cells, and notes anti-inflammatory activity at concentrations between 0.5% and 5%. It also reports that salicylic acid peels have been well tolerated across all skin types, which matters for anyone prone to dark marks. DermNet adds that salicylic acid softens keratin and helps loosen dry, scaly skin (DermNet).

For KP, salicylic acid helps but trailed lactic acid in the head-to-head trial. A 2020 systematic review still counted it among the topical treatments that improve KP’s appearance (Maghfour et al.). It is a strong choice when your bumps look more like dark, open pores than rough, dry plugs.

One caution: salicylic acid can be absorbed through the skin. DermNet notes that it shouldn’t normally be used on children under 2 and that you should tell your doctor if you’re pregnant or breastfeeding. Toxicity from topical use is rare; Arif’s review notes it has been reported when a 20% preparation was applied to half the body’s surface.

Lactic vs. glycolic vs. salicylic acid at a glance

Acid	Type	Best match	Main trade-off
Lactic acid	AHA, water-soluble	Keratosis pilaris, dry and rough skin	Mild stinging; increases sun sensitivity
Glycolic acid	AHA, smallest molecule	Thick, rough texture; razor bumps	Most likely to sting; increases sun sensitivity
Salicylic acid	BHA, oil-soluble	Clogged pores, strawberry legs, bumps after shaving	Avoid in young children; check with a doctor in pregnancy

Matching the acid to your bumps

• Rough, dry bumps on the upper arms or thighs (KP): start with lactic acid or urea. Our weekly KP routine for arms shows where it fits.
• Dark dots on shaved legs (strawberry legs): salicylic acid is the logical first try, sometimes alternating with an AHA. See exfoliating for strawberry legs.
• Bumps from shaving or ingrown hairs: glycolic or salicylic acid between shaves can help keep hairs from getting trapped. See ingrown hairs on your legs.
• Itchy, uniform bumps on the chest and back, or pus-filled bumps: these may be folliculitis or Malassezia folliculitis. Acids don’t treat infections; get a diagnosis.

How to use body acids safely

1. Use one acid at a time. Layering several exfoliants is the fastest route to irritation. The AAD also advises against exfoliating while using retinoids, retinol or benzoyl peroxide unless your dermatologist has planned it (AAD).
2. Start slowly. Use it every other day for the first couple of weeks, then increase if your skin is comfortable.
3. Apply to dry, intact skin and moisturize. Never apply acids to cut, freshly shaved, broken or sunburned skin.
4. Protect from the sun. The FDA recommends sunscreen, protective clothing and limited sun exposure while using AHAs and for a week afterward.
5. Be cautious with darker skin. The AAD advises avoiding strong chemical or mechanical exfoliation on darker skin tones or skin with dark spots, because aggressive exfoliation can increase pigmentation.

For leave-on AHA cosmetics, the FDA cites an expert panel’s conclusion that products are safe at a concentration of 10% or less with a final pH of 3.5 or higher. Stronger concentrations belong in a professional’s hands.

When to see a dermatologist

If over-the-counter acids haven’t helped after six to eight weeks, a dermatologist can confirm what the bumps are and offer stronger options. Our red-flag checklist explains which bumps shouldn’t wait.

Frequently asked questions

Is lactic acid or glycolic acid better for keratosis pilaris?

Lactic acid has better direct evidence for KP and also helps skin hold moisture, which suits the dry, rough texture of KP. Glycolic acid also exfoliates well, and the AAD lists both. If your skin is sensitive, lactic acid is usually the gentler starting point.

Can I use salicylic acid and lactic acid together?

Some products combine them at low concentrations. If you’re using separate products, alternating days is gentler than layering. Watch for stinging, redness or peeling, and cut back if they appear.

How long does lactic acid take to work on KP?

In the 12-week trial, lesion counts dropped significantly by week 4 and continued to improve through week 12. The AAD suggests talking to your dermatologist if there’s no improvement after four to six weeks of consistent use.

Do acids work on razor bumps?

Glycolic and salicylic acid can help by keeping dead skin from trapping regrowing hairs, and glycolic acid may reduce hair curvature. They work best alongside better shaving technique.

Is salicylic acid safe to use all over the body?

For most adults, using a body product as directed is fine. DermNet warns that salicylic acid can be absorbed through the skin, shouldn’t normally be used on children under 2, and should be discussed with a doctor during pregnancy or breastfeeding.

Sources

1. Kootiratrakarn T, Kampirapap K, Chunhasewee C. “Epidermal permeability barrier in the treatment of keratosis pilaris.” Dermatology Research and Practice, 2015. source
2. Feng X, Shang J, Gu Z, Luo X, Chen Y, Liu Y. “Lactic acid chemical peeling in skin disorders.” Clinical, Cosmetic and Investigational Dermatology, 2024. source
3. Moghimipour E. “Hydroxy acids, the most widely used anti-aging agents.” Jundishapur Journal of Natural Pharmaceutical Products, 2012. source
4. Arif T. “Salicylic acid as a peeling agent: a comprehensive review.” Clinical, Cosmetic and Investigational Dermatology, 2015. source
5. Ogunbiyi A. “Pseudofolliculitis barbae; current treatment options.” Clinical, Cosmetic and Investigational Dermatology, 2019. source
6. Maghfour J, Ly S, Haidari W, Taylor SL, Feldman SR. “Treatment of keratosis pilaris and its variants: a systematic review.” Journal of Dermatological Treatment, 2022. source
7. DermNet. “Salicylic acid.” DermNet NZ. source
8. U.S. Food and Drug Administration. “Alpha hydroxy acids.” FDA.gov. source
9. American Academy of Dermatology. “Keratosis pilaris: Diagnosis and treatment.” AAD.org. source
10. American Academy of Dermatology. “How to safely exfoliate at home.” AAD.org. source

This article is for general information and isn’t a substitute for professional medical advice, diagnosis or treatment.