AHA

What is AHA?

AHA is short for alpha hydroxy acids. Because many of them occur naturally in fruit, milk or sugar cane, they are also called fruit acids. They are water-soluble and work mainly on the skin’s surface. The most important AHAs in skincare:

• Glycolic acid – the smallest molecule, penetrates deepest and is the strongest
• Lactic acid – gentler and also hydrating
• Mandelic acid – a large molecule, very mild, good for sensitive skin
• Citric, tartaric and malic acid – often included in combinations

Closely related are the even gentler PHAs (polyhydroxy acids) such as gluconolactone, which K-beauty often uses together with AHA and BHA.

How does AHA work on the skin?

• Exfoliation: AHAs loosen the bonds between dead skin cells so they shed more easily.
• Glow: The skin looks smoother, fresher and more radiant.
• Dark spots: Post-acne marks and sun spots fade faster.
• Skin texture: Rough patches and fine lines are softened.
• Absorption: After exfoliation, the serums that follow can absorb better.

Which skin types is AHA suitable for?

• dull, tired skin – see Glow skincare
• skin with dark spots and post-acne marks – see Dark spots
• dry, rough skin – lactic acid in particular
• mature skin with fine lines

Sensitive skin is best off starting with mandelic acid or PHA. With rosacea, eczema or irritated skin, you should avoid AHA.

How to use AHA

1. In the evening, cleanse your face and let your skin dry.
2. Apply an AHA toner, pad or serum.
3. Finish with a soothing, hydrating moisturiser.
4. Always use sunscreen in the morning – AHAs make the skin more sensitive to light.

Start with two to three applications a week and a low concentration (around 5 to 8% glycolic acid). A slight tingling is normal; strong burning or redness is not.

What can you combine AHA with?

• Hyaluronic acid for hydration after exfoliating
• Niacinamide for an even complexion
• Ceramides, panthenol and Centella Asiatica for strong, calm skin

Don’t use it in the same evening as retinol, retinal, strong BHA or pure vitamin C. Ready-made AHA/BHA/PHA combinations, on the other hand, are formulated to be well tolerated.

AHA in Korean skincare

Korean brands focus on gentle AHA exfoliation for daily use: toner pads, exfoliating toners and mild combinations of AHA, BHA and PHA. Well-known examples include the AHA, BHA, PHA 30 Days Miracle line from SOME BY MI, the AHA/BHA Clarifying Treatment Toner from COSRX, the Green Plum Refreshing Toner from Beauty of Joseon and medicube’s Zero Pore Pads. Our Korean AHA skincare collection has all products with AHA.

What does the research say?

AHAs are among the longest-studied exfoliating ingredients. In a clinical study, glycolic and lactic acid improved skin texture in sun-damaged skin and increased skin thickness (Ditre et al., Journal of the American Academy of Dermatology, 1996). A review describes the different hydroxy acids and stresses that they can increase sensitivity to light – so sun protection is a must (Kornhauser et al., Clinical, Cosmetic and Investigational Dermatology, 2010).