The Ordinary Mandelic Acid 10% + HA - Gentle exfoliation for radiant and even skin. The Ordinary Mandelic Acid 10% + HA is a highly effective but particularly gentle exfoliating formula that refines the skin's texture, evens out the complexion and provides a fresh glow. With 10% mandelic acid (AHA) and hyaluronic acid-based moisturiser, this serum removes dead skin cells without causing irritation - ideal for sensitive skin. What makes mandelic acid so special? Mandelic acid is one of the alpha hydroxy acids (AHAs), but has a larger molecular structure than other acids such as glycolic or lactic acid. As a result, it acts more slowly and gently, while still being effective against uneven, dull skin and fine lines.