AHA – Alpha-Hydroxy Acids: Effects, Exfoliating Properties, and Application in Skincare

Alpha-hydroxy acids are among the most thoroughly researched active ingredients in modern skincare. Their ability to refine the skin surface and support cell regeneration makes them a staple in many skincare routines. Those who want to both protect the skin barrier and exfoliate effectively should be familiar with the properties of this group of active ingredients.

What are Alpha-Hydroxy Acids?

Alpha-hydroxy acids – or AHA for short – are water-soluble organic acids that occur naturally in various foods. Key examples include glycolic acid (from sugarcane), lactic acid (from fermented dairy products), mandelic acid (from bitter almonds), and malic acid (from fruits). In cosmetics, they are used for their keratolytic effect: they weaken the ionic bonds between dead skin cells in the stratum corneum, enabling controlled exfoliation without mechanical friction.

How do AHAs affect the skin?

The mechanism of action is pH-dependent. AHAs lower the pH value on the skin surface, displacing calcium ions from the connections between corneocytes – allowing dead skin cells to shed in a controlled manner. Glycolic acid, with its small molecular size, has the strongest penetration ability; mandelic acid penetrates more slowly due to its larger molecular structure and is therefore considered more tolerable for sensitive skin. Lactic acid also has a humectant effect: it binds moisture in the stratum corneum and supports the skin's natural moisturizing complex.

Benefits and Effects of AHA

Regular use can visibly refine the complexion, reduce irregularities, and make the skin texture appear more even. Scientific studies show that glycolic acid can stimulate collagen synthesis in dermal fibroblasts. Additionally, chemically exfoliated skin facilitates the penetration of subsequent active ingredients: products with hyaluronic acid or vitamin C can be absorbed more effectively after an AHA application.

Application and Tolerability

For home use, AHAs are employed in concentrations of 5–15%. Higher concentrations are reserved for professional treatments. A gradual introduction is recommended: 2–3 applications per week in the evening, allowing the skin to adapt slowly. AHAs increase the skin's photosensitivity – broad-spectrum sunscreen with at least SPF 30 is absolutely essential for daytime use with regular application. For sensitive or reactive skin, lower concentrations are preferable.

Combination with Other Active Ingredients

AHAs combine well with humectants such as glycerin and hyaluronic acid, as these counteract a potential drying effect after exfoliation. Direct combination with retinol or highly potent oxidizing agents should be avoided, as irritation may occur. A staggered application is more sensible: AHAs in the evening, retinol on alternating evenings. Antioxidants like vitamin C ideally complement the morning routine.

Who are AHAs suitable for?

AHAs are suitable for most skin types – especially for mature skin, skin with an uneven complexion, keratinization disorders, and minor pigment changes. In cases of active rosacea, acute skin irritations, or a compromised skin barrier, application should be paused and medical advice sought.

Frequently Asked Questions about AHA

How often should one use AHA?

For beginners, 2–3 applications per week in the evening are recommended. As the skin becomes accustomed, the frequency can be individually increased – depending on concentration, product, and personal reaction.

Can AHA and BHA be combined?

Yes. AHAs work on the skin surface, while BHAs like salicylic acid penetrate deeper into the pores as oil-soluble acids. Both principles of action complement each other; however, a slow introduction is advisable.

Do AHAs permanently increase UV sensitivity?

No, not permanently. During an active AHA regimen, photosensitivity is increased. Daily sun protection during the application phase is obligatory; after discontinuation, light sensitivity normalizes.

Are AHAs suitable for sensitive skin?

Conditionally. Lactic or mandelic acid in low concentrations (5–8%) are often well tolerated. Sensitive skin should initially avoid glycolic acid in high concentrations.

Conclusion

Alpha-hydroxy acids are well-researched, versatile active ingredients that, when used correctly, can sustainably refine the skin's appearance. Concentration, frequency, and consistent sun protection are the crucial parameters for a tolerable integration into the skincare routine.

The Porcelain Skin Serum is an ideal complementary skincare solution for daily routine.

Current scientific findings underscore the importance of AHAs for a well-founded, sustainable skincare strategy (as of 2025).

The Blue Crystal Drops strengthen the skin barrier through a balanced combination of moisturizing and protective active ingredients.

Sources

• DermNet NZ – Glycolic acid
• PubMed – Alpha-Hydroxy-Acids Research