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Salicylic Acid
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What Is Salicylic Acid in Skincare?
Salicylic acid is a beta hydroxy acid (BHA), a chemical exfoliant that loosens the bonds between dead surface cells so they shed more evenly. Unlike water-soluble alpha hydroxy acids such as glycolic acid, salicylic acid is oil-soluble, so it can work into oily, congested pores. That is why it is the classic exfoliant for oily and combination skin, blackheads and pores that look enlarged.
EWG Skin Deep rating for Salicylic Acid
Quick Facts
| Property | Detail |
|---|---|
| INCI name | Salicylic Acid (2-hydroxybenzoic acid) |
| Common names | BHA, beta hydroxy acid; related botanical: willow bark extract (Salix alba), which contains salicin, not salicylic acid itself |
| Source | Usually made synthetically; originally identified from willow bark and wintergreen |
| Form | White crystalline powder |
| Solubility | Poor in water; dissolves in alcohol, propanediol, glycols and some oils |
| Typical usage rate | Up to 2% in most cosmetic products under EU rules (0.5% in body lotions and eye or lip products, 3% in rinse-off hair products) |
| pH | Works best around pH 3 to 4; the human study cited below used 2% at pH 3.5 |
| Skin types | Oily, combination and congested looking skin; use with care on dry or sensitive skin |
How Salicylic Acid Works on the Skin
Salicylic acid softens the "glue" that holds dead cells together in the outer layer of skin and inside the pore lining. Because it is lipophilic (oil-loving), it mixes with sebum and reaches places water-based acids do not. The visible result is smoother texture, fewer blackheads and pores that look cleaner and smaller.
Salicylic acid and sun sensitivity
All exfoliating acids raise a fair question: do they make skin burn more easily? A 2009 study by Kornhauser and colleagues in the Journal of Dermatological Science tested this in 14 healthy volunteers aged 24 to 59. Each person had test sites that received 10% glycolic acid (pH 3.5), 2% salicylic acid (pH 3.5), the base alone, or nothing, once a day on weekdays for 3.5 weeks, then exposed to simulated sunlight. Glycolic acid increased redness, sunburn cells and DNA damage markers. Salicylic acid did not differ significantly from the base or untreated skin. The authors concluded that 2% salicylic acid did not increase skin's sensitivity to the simulated sunlight, while 10% glycolic acid did. Daily sunscreen is still essential with any exfoliant.
Salicylic acid vs. glycolic acid
| Feature | Salicylic acid (BHA) | Glycolic acid (AHA) |
|---|---|---|
| Solubility | Oil | Water |
| Where it works | Surface and inside oily pores | Surface |
| Best for | Oily skin, blackheads, enlarged-looking pores | Dullness, uneven tone, rough texture |
| Sun sensitivity in the 2009 study | No significant increase at 2% | Increased at 10% |
How to Use Salicylic Acid in Formulas
- Dissolve it first. Salicylic acid powder will not dissolve in plain water. Dissolve it in propanediol, glycerin with gentle warming, or alcohol before adding it to the water phase.
- Check pH. Salicylic acid's pKa is about 3, so the exfoliating free acid form dominates near pH 3 and drops off quickly above pH 4. Target pH 3.5 to 4 and measure with a pH meter, not strips.
- Watch for crystals. If a toner turns cloudy or grows needle-like crystals, the acid has come out of solution. Use enough solvent (about 5 parts propanediol per part acid), avoid storing it cold, and do not add extra water after dissolving.
- Stay within the limit. 2% is the ceiling for face products under EU rules. More is not better and increases dryness.
- Where it fits. Cleansers and toners give short contact; leave-on serums and gels give stronger results.
- Do not use on children under 3, and avoid it if you have an aspirin allergy.
- Storage. Keep powder sealed and dry. Finished products need a preservative that works at low pH.
Simple 2% salicylic toner (100 g)
Dissolve 2 g salicylic acid in 10 g propanediol, warming gently (below 50°C / 122°F) and stirring until clear. Add it to 86 g distilled water, then 1 g of a preservative rated for low pH and 1 g glycerin. Stir, check pH and adjust to 3.5 to 4 if needed. Apply with a cotton pad to the T-zone in the evening, starting 3 nights a week.
What to expect
Skin often feels smoother after the first few uses. Changes in blackheads and the look of pores usually take 4 to 8 weeks of steady use, because the pore lining renews gradually. Mild dryness or flaking in the first two weeks is common; pull back to every other day and add a light moisturizer rather than stopping.
Who Salicylic Acid Suits
Salicylic acid suits oily and combination skin and anyone with blackheads or congested looking pores. Dry skin can use it as a spot exfoliant on the T-zone. Sensitive skin: patch test on the inner arm for 24 hours, start at the lowest rate (0.5%), use it 2 to 3 times a week, and work up only if skin stays comfortable. Pregnant or nursing? Ask your doctor first.
Frequently Asked Questions
Is salicylic acid good for large pores?
Yes. Because it is oil-soluble, it clears oil and dead cells from inside the pore, so pores look smaller and cleaner. Results build over 4 to 8 weeks of steady use.
Can I use salicylic acid every day?
Many oily skin types can. Start every other day and increase if skin is not dry or tight. Always follow with a moisturizer and use daily sunscreen.
Can I use salicylic acid with retinol or glycolic acid?
Use them at different times, for example salicylic acid in the morning and retinol at night. Stacking several exfoliants at once can leave skin dry and irritated looking.
Does salicylic acid dry out skin?
It can, especially above 1% or with daily leave-on use. Follow with a moisturizer that contains humectants such as hyaluronic acid or glycerin.
Does salicylic acid make skin more sensitive to the sun?
In a 2009 study of 14 volunteers, 2% salicylic acid did not significantly increase sunburn response, while 10% glycolic acid did. Daily sunscreen is still essential with any exfoliant.
Is willow bark the same as salicylic acid?
No. Willow bark contains salicin, a gentler related compound, at much lower and more variable levels.
Shop and Learn More
For a gentle daily exfoliating cleanse, try our Alpha Hydroxy Probiotic Cleanser, shown below with this collection. For a full comparison, read Glycolic vs Salicylic Acid: Which Is Right For You?. Related entries: glycolic acid, large pores and witch hazel.
Sources
- Kornhauser A, Wei RR, Yamaguchi Y, et al. The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin. Journal of Dermatological Science. 2009;55(1):10-17. PMC2791365
- Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clinical, Cosmetic and Investigational Dermatology. 2010;3:135-142. doi:10.2147/CCID.S9042
- EU Cosmetics Regulation, Annex III entry for salicylic acid (Regulation (EU) 2021/850): 3% rinse-off hair, 0.5% body lotion, eye and lip products, 2% other products. Summary at coslaw.eu
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.
About the Author
Written by Kari Thomas, cosmetic formulator and founder of Skin Perfection.