Salicylic acid (BHA): What really works for acne and blocked pores

Salicylic acid, referred to in scientific literature as a beta-hydroxy acid (BHA), is a lipophilic organic acid that penetrates sebum-filled pores and dissolves plugs of oil. It is most useful for oily skin, acne-prone skin, blackheads and seborrhoea. Caution is needed with dry, dehydrated skin and active rosacea. At Dulcia, we have not included salicylic acid in our current range, and we explain why below. This article explores how BHA works at a cellular level, which concentrations are worthwhile and why two products with the same content can differ in effectiveness.

What is salicylic acid?

Salicylic acid is ortho-hydroxybenzoic acid: an organic molecule with hydroxyl (OH) and carboxyl (COOH) groups on an aromatic benzene ring. In nature, it is found mainly in willow bark (Salix alba). Modern cosmetics use two forms: isolated synthetic acid and plant-derived willow extract, which contains its precursor, salicin.
It differs from aspirin (acetylsalicylic acid) by a single acetyl group, but their effects on the skin are different. Aspirin is a systemic analgesic and antipyretic, while topical salicylic acid is a comedolytic ingredient with mild anti-inflammatory properties. The molecule has a pKa of approximately 2.97 and a log P of around 2.35, making it a weak acid with pronounced lipophilicity. It has a history of more than 2,000 years of use in topical dermatological skincare (Arif, Clin Cosmet Investig Dermatol, 2015).

Willow bark versus synthetic salicylic acid: what is the difference?

Willow bark contains the glycoside salicin, which enzymes in the body convert into salicylic acid. In topical cosmetics, however, this conversion is incomplete, so 0.5% salicin is not equivalent to 2% synthetic salicylic acid. Both have a place in skincare, but their roles differ.
Salicin has a glucose molecule attached to its benzene ring, which β-glucosidases and alcohol dehydrogenase must gradually convert via saligenin into salicylic acid. In the skin, this conversion is slower and incomplete. Willow extract also contains other phenolic compounds, polyphenols and flavonoids, which form a mildly anti-inflammatory complex rather than a single-molecule precursor to salicylic acid (Shara & Stohs, Phytother Res, 2015).
The clinical evidence for salicin is more limited, but it does exist. In a study by Gopaul and colleagues involving 29 women, applying a serum containing 0.5% salicin twice daily for 12 weeks produced statistically significant improvements in skin texture, pore size, pigmentation and overall appearance, with no reported tolerability reactions (Gopaul et al., J Cosmet Dermatol, 2010).
Willow extract is gentler and suitable for sensitive skin or for targeting the signs of ageing. Synthetic salicylic acid at a concentration of 1 to 2% has a stronger comedolytic effect and dissolves plugs of oil in acne more directly.

How BHA works on the skin: lipophilicity and pores

Salicylic acid is oil-soluble (log P ≈ 2.35), so it penetrates from the skin's surface into sebum-filled pores and sebaceous glands, where it dissolves comedones and clears blockages. This physical difference from AHAs, which are hydrophilic and work on the surface, explains why BHA is a first choice for oily, acne-prone skin.
It works in three ways at once within the skin. Its desmolytic action disrupts desmosomes, the ‘glue’ between corneocytes in the stratum corneum, allowing older cells to shed gradually (Arif, 2015). Its comedolytic action dissolves the plug of oil inside the follicle, which AHAs cannot reach because of their hydrophilic nature. And as a salicylate, it mildly reduces inflammation: it inhibits the synthesis of certain prostaglandins and reduces the local inflammatory response.
Unlike AHAs, salicylic acid does not increase skin photosensitivity. In a comparative study, Kornhauser and colleagues showed that 10% glycolic acid increased human skin sensitivity to simulated sunlight, while 2% salicylic acid did not; in an animal model, it even showed a mild photoprotective effect (Kornhauser et al., Clin Cosmet Investig Dermatol, 2010). Morning SPF is nevertheless essential, as renewed skin is more sensitive overall.

What are the differences between AHA and BHA?

AHAs (alpha-hydroxy acids) work in a water-based environment on the surface of the stratum corneum and are most effective for pigmentation, fine lines, photoageing and drier skin. BHA (salicylic acid) works in the oily environment of pores and sebaceous glands and is the choice for acne, blackheads and oily skin. They can coexist in a skincare routine, typically on alternate days. 

Comparison in brief: AHA for smoothness and tone, BHA for pores. For combination skin, these two groups are often alternated, and there is no need to use both in the routine at the same time.

Which concentration and pH are worthwhile?

In cosmetics, salicylic acid is used at concentrations of 0.5 to 2%. However, its effectiveness does not depend solely on the percentage: the formulation's pH is decisive. At a pH of around 3.0, 50% is in its active, undissociated form; above pH 4.0, it rapidly loses effectiveness. Two products with the same SA content can therefore differ substantially in their actual effectiveness.

Over-the-counter concentration guide:
• 0.5% is a gentle maintenance concentration, suitable for more sensitive skin or first-time use.
• 1% is a medium-strength concentration, which most good-quality OTC serums and toners aim for.
• 2% is the upper limit for cosmetic use, most commonly found in acne products.
• 20 to 30% are peel concentrations for use in dermatology clinics. In 2023, Liang and colleagues studied a 30% supramolecular peel (28 patients, 4 sessions over 8 weeks) and recorded a marked improvement in GAGS acne scores in 57.1% of patients and a mild improvement in 42.9% (Liang et al., Dermatol Ther, 2023).
• 30 to 40% are used in medical applications (warts, corns), outside cosmetics.

The clinical evidence for a 2% concentration is strong. In 1992, Zander and Weisman published a series of three placebo-controlled studies in which 2% salicylic acid pads significantly reduced primary comedones and, consequently, the number and severity of inflammatory lesions (Clin Ther, 1992). In a multicentre study by Ye and colleagues (2024), 2% supramolecular salicylic acid achieved a 51% rate of ‘regression and marked improvement’ over 12 weeks, which was not significantly worse than adapalene gel (43%, p = 0.0831). A split-face study by Dai and colleagues showed a reduction of 47.9% in papules and pustules, 43.1% in non-inflammatory lesions and 44.1% in total lesions over 28 days (J Cosmet Dermatol, 2019).
If the label says ‘2% salicylic acid’ but the product has a pH of 5 or 6 (typical of gentle creams), only a small proportion is in the active form. An effective BHA formulation needs a pH between 3.0 and 3.5.

Who can benefit from BHA, and who should avoid it?
Salicylic acid is most useful for oily skin, acne-prone skin, blackheads, seborrhoea and keratosis pilaris. It is less suitable for dry, dehydrated skin, active papulopustular rosacea and a thin, irritated skin barrier.

Suitable uses:
• Oily skin and comedonal acne: targeted application of 0.5 to 2% to the T-zone, 2 to 3 times a week; its lipophilicity allows it to enter the sebum plug directly.
• Facial seborrhoea: salicylic acid softens and loosens greasy flakes; see the guide to seborrhoeic dermatitis for more details.
• Keratosis pilaris on the body: body creams containing 1 to 2%, combined with urea or lactic acid.
• Post-inflammatory acne marks (PIH): complements azelaic acid and niacinamide; see the guide to pigmentation marks for details.
Unsuitable, or use with caution:
• Dry, dehydrated skin: ideally 0.5%, no more than once a week, using the sandwich method.
• Active papulopustular rosacea: we choose azelaic acid and niacin, not BHA; see the rosacea guide for more information.
• A thin, irritated barrier after retinols or peels: restore the barrier first, then consider BHA.
• Active eczema, open lesions, damaged skin: avoid.

At Dulcia, we chose a different path: why BHA is not in our current range

At Dulcia, we have not included salicylic acid in our current range. When developing Plus First Aid for Acne and Acne Face Cream with a Cleansing Complex, we deliberately chose a different trio of active ingredients: zinc (Zinc PCA and zinc oxide) as an antimicrobial and sebum-regulating foundation, azelaic acid to target inflammation and pigmentation, and shikimic acid with an AHA complex (glycolic, lactic and citric acids) for gentle exfoliation. In a natural formulation with a low proportion of synthetic preservatives, maintaining the stable pH of 3.0 to 3.5 that salicylic acid needs for full effectiveness is technically demanding and limits the proportion of plant extracts that define our approach. Shikimic acid with an AHA complex works within a milder pH range. If you are specifically looking for a cosmetic BHA, we recommend adding one from a brand that formulates it properly. Transparency on this issue matters more than making a sale.

How to introduce BHA into your routine: frequency and gradual increases
Do not use BHA daily from day one. Start with a low concentration (0.5 to 1%) in the evening, 2 to 3 times a week, and gradually increase the frequency over 2 to 4 weeks. Morning SPF is essential. The first visible results (clearer pores, fewer comedones) appear after 4 to 8 weeks, with the full effect after approximately 12 weeks.
Suggested introduction schedule:
Weeks 1 to 2: a small amount on clean, dry skin in the evening, 2 times a week.
Weeks 3 to 4: in the evening, 3 times a week, if your skin tolerates the previous step without irritation.
Week 5: every other night.
4 Goal: nightly application, if your skin allows. Most people settle at 3 to 4 times a week, and that is fine.
For more sensitive skin, we recommend the sandwich method: a hydrating toner before BHA, followed by BHA, then a night cream. This slightly reduces penetration but improves tolerability during the first few weeks. Assess the initial results after 4 weeks and the final results after 12. Morning SPF is not optional: although salicylic acid itself does not increase photosensitivity (Kornhauser et al., 2010), renewed skin is generally more sensitive to UV radiation.

What to avoid: combinations and mistakes

Do not apply salicylic acid at the same time as retinol, AHAs or highly concentrated vitamin C. The aim is to separate them, either AM/PM or on alternate days. Also avoid BHA products with a pH above 4 and alcohol-based toners in the same routine.
• BHA and retinol in the same application: unnecessary cumulative irritation. Use retinol on some evenings and BHA on others. A typical schedule: retinol on Monday, Wednesday and Friday; BHA on Tuesday, Thursday and Saturday; a break on Sunday.
• BHA and AHA in the same application: rarely necessary. If using both, alternate days.
• BHA and L-ascorbic acid above 10%: they compete chemically. Vitamin C in the morning, BHA in the evening.
• BHA and niacinamide: niacinamide soothes, SA clears pores. A classic pairing for oily, acne-prone skin.
• BHA with active papulopustular rosacea: no; we choose azelaic acid and niacin.
• Products that list SA but have a pH above 4: even if the label says ‘2% salicylic acid’, only a small proportion is in the active form, and the effect is largely marketing.

Frequently asked questions

Is salicylic acid safe during pregnancy?
According to the American College of Obstetricians and Gynecologists (ACOG), low topical concentrations (up to 2%) applied to the face are considered acceptable during pregnancy, as only a small proportion of the dose is absorbed through local application. However, avoid higher concentrations (20 to 30% salicylic acid peels) and oral forms. If you have any doubts, consult your obstetrician or gynaecologist. Many pregnant customers choose to avoid BHA during pregnancy and return to it after giving birth, and that is a perfectly valid choice.

Does salicylic acid help with blackheads?
Yes. When applied to targeted areas at 0.5 to 2%, BHA is one of the most effective ingredients specifically for open comedones. Its lipophilicity allows it to enter sebum-filled pores and dissolve the plugs. In a clinical study by Dai and colleagues, 2% supramolecular salicylic acid reduced non-inflammatory lesions by 43.1% over 28 days (Dai et al., 2019). In practice, consistency matters more than the exact concentration: apply to the T-zone 2 to 3 times a week for at least 8 weeks.

What is the difference between AHA and BHA?
AHAs (glycolic, lactic and mandelic acids) are water-soluble and work on the surface of the stratum corneum. They are suitable for pigmentation, fine lines and drier skin. BHA (salicylic acid) is oil-soluble and can reach sebum-filled pores, making it the choice for acne, blackheads and oily skin. When used together in a routine, they are typically alternated on different days and do not need to be applied at the same time.

Can I combine salicylic acid with retinol?
In the same routine, yes; in the same application, no. Both are effective exfoliating ingredients, and applying them together unnecessarily increases irritation. A practical solution: retinol on some evenings, BHA on others. A typical schedule: retinol on Monday, Wednesday and Friday; BHA on Tuesday, Thursday and Saturday; a break on Sunday.

Can BHA dry out or irritate the skin?
Yes, most often when too much is used or it is combined with other exfoliants. Typical signs include temporary itching, tightness and mild flaking. The solution has three steps: reduce use to 2 times a week, apply using the sandwich method (a moisturising product before and after BHA), and temporarily remove retinol, AHAs and alcohol-based toner from the routine. For drier, sensitive skin, 0.5% is a better choice than 2%, or try a gentle willow extract.

How long does it take to see results?
The first improvements in texture and pore clarity are visible after 4 to 6 weeks of regular use (2 to 3 evenings a week). A significant reduction in comedones and mildly inflammatory lesions usually appears between weeks 8 and 12. In the study by Ye and colleagues (2024), 2% salicylic acid achieved a 51% rate of regression and marked improvement at week 12. BHA is not an ingredient for a one-week course; allow three months.

Conclusion

Salicylic acid is one of the most reliable ingredients in modern dermatological skincare for oily skin and acne, provided it is formulated correctly (pH 3.0 to 3.5) and used in a targeted way (0.5 to 2%, 2 to 3 times a week). At Dulcia, we have chosen a different path for our current range — zinc, azelaic acid and shikimic acid combined with an AHA complex — because this combination works reliably in our natural base without compromising the formulation. It is a conscious formulation choice, not an oversight. Give your skin the ingredient that is genuinely right for it, rather than the one that sounds best in an advert. Every box from us contains our thoughts, the work of our hands and our heart.

Sources

1 Arif T. ‘Salicylic acid as a peeling agent: a comprehensive review.’ Clinical, Cosmetic and Investigational Dermatology 2015; 8:455–461. PMID: 26347269. DOI: 10.2147/CCID.S84765.
2 Kornhauser A, Coelho SG, Hearing VJ. ‘Applications of hydroxy acids: classification, mechanisms, and photoactivity.’ Clinical, Cosmetic and Investigational Dermatology 2010; 3:135–142. PMID: 21437068. DOI: 10.2147/CCID.S9042.
3 Zander E, Weisman S. ‘Treatment of acne vulgaris with salicylic acid pads.’ Clinical Therapeutics 1992; 14(2):247–253. PMID: 1535287.
4 Ye X, Xiao Y, Liu T, et al. ‘2% supramolecular salicylic acid hydrogel vs. adapalene gel in mild to moderate acne vulgaris treatment: A multicenter, randomized, evaluator-blind, parallel-controlled trial.’ Journal of Cosmetic Dermatology 2024; 23(6):2119–2128. PMID: 38590107. DOI: 10.1111/jocd.16238.
5 Dai H, Hu D, Li Y, et al. ‘Efficacy and safety of 2% supramolecular salicylic acid compared with 5% benzoyl peroxide/0.1% adapalene in the acne treatment: A randomized, split-face, open-label, single-center study.’ Journal of Cosmetic Dermatology 2019. PMID: 30173582.
6 Liang J, Shao Y, Wu L, et al. ‘Effect of 30% Supramolecular Salicylic Acid Peel on Skin Microbiota and Inflammation in Patients with Moderate-to-Severe Acne Vulgaris.’ Dermatology and Therapy 2023; 13(1):155–167. PMID: 36350527. DOI: 10.1007/s13555-022-00844-5.
7 Gopaul R, Knaggs HE, Lephart JD, Holley KC, Gibson EM. ‘An evaluation of the efficacy of a topical product containing salicin for the reduction of the visible signs of aging.’ Journal of Cosmetic Dermatology 2010; 9(3):192–199. PMID: 20883292. DOI: 10.1111/j.1473-2165.2010.00505.x.
8 Shara M, Stohs SJ. ‘Efficacy and Safety of White Willow Bark (Salix alba) Extracts.’ Phytotherapy Research 2015; 29(8):1112–1116. PMID: 25997859. DOI: 10.1002/ptr.5377.
9 American College of Obstetricians and Gynecologists (ACOG). ‘Skin Conditions During Pregnancy.’ FAQ sheet, acog.org. Accessed April 2026.
10 European Commission. Regulation (EC) No 1223/2009, Annex V (preservatives: salicylic acid ≤ 0.5%) and Annex III (restricted substances). Consolidated version 2026