AHA, BHA, or PHA? Difference, Use, and Selection Based on Skin Type
Pharmacist Berfin Işık prepared this article. As a pharmacist and cosmetic science expert, she specializes in skincare ingredients. This content is for informational purposes only and does not constitute medical advice.
AHA, BHA, or PHA? If you're standing in front of a shelf trying to decide which acid to choose, you're not alone. In this guide, we explain what AHAs, BHAs, and PHAs are, how they work, and which one you should choose based on your skin type, supported by scientific data.
What are AHA, BHA, and PHA? Chemical Structure and Key Differences
Hydroxy acids are among the most extensively researched and widely used chemical exfoliant compounds in cosmetics. The main distinction between the three groups lies in whether the molecule is fat-soluble or water-soluble, and its molecular size.
- AHA (Alpha Hydroxy Acid): Water-soluble, works on the surface of the epidermis.
- BHA (Beta Hydroxy Acid): Fat-soluble, penetrates into the follicular canal.
- PHA (Polyhydroxy Acid): Due to its large molecular structure, it only acts on the surface of the stratum corneum; it is the group with the lowest irritation potential.
AHA (Alpha Hydroxy Acid)
Alpha hydroxy acids are organic acids derived from natural sources, such as glycolic acid, lactic acid, and mandelic acid. They disrupt the corneocyte cohesion mechanism in the outermost layer of the stratum corneum, allowing dead cells to shed. A review by Tang and Yang shows that AHAs also thicken the dermal layer by increasing glycosaminoglycan synthesis.
BHA (Beta Hydroxy Acid)
The main compound is salicylic acid. Its fat solubility allows it to penetrate the follicular canals clogged by sebaceous glands, dissolving the sebum-keratin mixture.
PHA (Polyhydroxy Acid)
PHAs are second-generation members of the AHA family. Due to their large molecular weight, they work on the superficial layer of the stratum corneum; their irritation potential is significantly lower compared to AHAs.
AHA, BHA, and PHA Comparison Table
| Feature | AHA | BHA | PHA |
|---|---|---|---|
| Solubility | Water | Oil | Water |
| Penetration | Medium-deep | Deep (follicle) | Superficial |
| Target Concern | Dead cells, spots, wrinkles | Sebum, acne, large pores | Gentle renewal, hydration |
| Irritation Risk | Medium | Very low-medium | Very low |
| Ideal Skin Type | Normal, dry, mature | Oily, acne-prone | Sensitive, rosacea, beginner |
Selection Guide by Skin Type
Oily and acne-prone skin: BHA (salicylic acid) should be the primary choice.
Dry and mature skin: AHA formulas containing lactic acid or glycolic acid are suitable.
Sensitive, red, and reactive skin: PHA, especially gluconolactone or lactobionic acid, is recommended.
Combination skin: A combination of BHA in the T-zone and AHA or PHA on the cheeks is suitable.
AHA / BHA / PHA Products at Medicblu
The verified products below cover different acid types and skin needs: from gentle PHA to BHA combinations suited to oily/acne-prone skin. If you are new to acids, start with 2-3 evenings a week and always use SPF during the day.
Conclusion
The right acid, with regular use, can provide measurable improvement within weeks. If you're unsure which acid is right for your skin, you can benefit from Medicblu's expert consultation service.
Scientific References
- Tang SC, Yang JH. Dual Effects of Alpha-Hydroxy Acids on the Skin. Molecules. 2018;23(4):863. PMID: 29642579
- Moghimipour E. Hydroxy Acids, the Most Widely Used Anti-aging Agents. Jundishapur J Nat Pharm Prod. 2012;7(1):9-10. PMID: 24624144
- Grimes P, Green BA, Wildnauer RH, Edison BL. The use of polyhydroxy acids (PHAs) in photoaged skin. Cutis. 2004;73(2 Suppl):3-13. PMID: 15002656
- Edison BL, et al. A polyhydroxy acid skin care regimen provides antiaging effects comparable to an alpha-hydroxyacid regimen. Cutis. 2004;73(2 Suppl):14-17. PMID: 15002657
- Arif T. Salicylic acid as a peeling agent: a comprehensive review. Clin Cosmet Investig Dermatol. 2015;8:455-461. PMID: 26347269
- Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol. 2010;3:135-142. PMID: 21437068
