Key etiologic factors include a genetic predisposition, solar damage, barrier abnormalities, and unique sensitivities to hormonal changes including pregnancy, oral contraceptives, and hormone replacement therapy .Melasma can be divided into centrofacial, malar, and mandibular, according to the pigment distribution on the skin. The hyperpigmented patches are usually symmetrical and have a sharp irregular border.On wood's light examination three forms of melasma exist (epidermal, dermal, and mixed). Epidermal \& mixed types shows accentuation of pigmentation, while there is no change in dermal type The epidermal type is the most responsive to treatment .Melasma is often difficult to treat, and the condition may be refractory. Principles of therapy include protection from ultraviolet light, inhibition of melanocyte activity and melanin synthesis, and the disruption and removal of melanin granules .Many depigmenting agents and other therapies such as chemical peeling are used for treating melasma, in the form of monotherapy or combined therapy .The most commonly used peeling agents are alpha-hydroxy-acids, glycolic acid , Jessner solution, salicylic acid resorcinol,trichloroacetic acid , pyruvic acid and phenol Several hypopigmenting agents such as topical hydroquinone (2 to 4%) alone or in combination with tretinoin (0.05 to 0.1%) have been used with differing results. Topical azelaic acid (15 to 20%) can be as efficacious as hydroquinone. Kojic acid, alone or in combination with glycolic acid or hydroquinone, has shown good results, due to its inhibitory action on tyrosinase. Chemical peeling is apromising treatment for numerous pigmentary disorders as melasma.Which aim to remove the melanin ,rather than the inhibition of melanocytes or melanogenesis by causing controlled necrosis and subsequent regeneration of the epidermis ,apart from remodeling of collagen and elastic fiberes in the dermis . The gold standard for chemical peeling agents is trichloroacetic acid It is a traditional chemical substance which has been used for both superficial and medium-depth as well as deep peelings.It is not expensive, stable, not light-sensitive and does not need to be neutralized .Classic Jessner's solution is a combination of different chemical substances, including salicylic acid(14gm), resorcinol(14gm), lactic acid(14gm) and ethanol, which can be used either alone for superficial peeling or in combination with other agents to make easier medium-depth procedures. Dr.Max Jessner originally formulated this peel to reduce the concentration and toxicity of each of the individual ingredients while increasing efficacy. Modified formula: lactic acid(17%), salicylic acid(17%), citric acid(8%) and ethanol .It is preferred , to avoid possible allergic reactions and hyperpigmentation problems, which may be created by resorcinol, especially in skin types V and VI.Gary Monheit has popularized the combination peel using the classic Jessner's solution combined with trichloroacetic acid , to achieve a more uniform penetration and an excellent peel with a low, safe concentration of trichloroacetic acid Glycolic acid it is one of the most frequently used superficial peeling agent.

It is stable , not light sensitive, inexpensive and easy to administer. Generally it is safe; scarring uncommon; persistent erythema and postpeel hyperpigmentation rarely seen.The depth of a Glycolic acid peel is a function of the concentration,volume and duration of application.Glycolic acid has been used in combination with trichloroacetic acid peels .70% glycolic acid is applied to the skin for 2 minutes.This is then neutralized,followed by the application of 35% trichloroacetic acid peels without any prior acetone scrub.This combination is thought to produce greater neoelastogenesis and less inflammation than Jessner/trichloroacetic acid combination.