Mandelic acid is an AHA obtained from the hydrolysis of bitter almond extract, it is a non toxic substance. It is a 8-carbon-alpha-hydroxy acid (AHA), with chemical formula of HOCH (C6H5) COOH. Its pK is 3.41, stronger than glycolic acid that instead has a pK of 3.83. The interesting fact about mandelic acid is its double nature as an AHA, because of its potential as a dermo-cosmetic, and the antibacterial action. The chemical peeling action of mandelic acid produces much less erythema, crusts and swellings and other effects, if compared to glycolic acid. The possible development of erythema is more gradual and foreseeable; probability of breakouts of hotspots in the dehydrated skin areas is minimal. Remarkably significant is the possibility for the patient to expose herself to the sun without any contraindications. One weekly mandelic peeling treatment is satisfactorily tolerated and has proved to be effective in particular against acne, melasma, freckles, all kinds of damages caused by photo-ageing (creases, wrinkles, structure diseases) and skin ageing. Skin exfoliation is gradual, thinly dandrufy (easily remediable using moisturizing creams), which is lasting for a number of days but never irritating or evident.