To compare the efficacy and safety of cryopeeling (using Liquid Nitrogen) and tranexemic acid (cyclokapron) versus chemical peeling (using TCA 20%) in treatment of melasma.

Melasma is a common, acquired, circumscribed hypermelanosis of the sun-exposed skin, It presents as symmetric, hyperpigmented macules having irregular, serrated, and geographic borders , The most common locations are the cheeks, upper lips, the chin and the forehead, but other sun-exposed areas may also be occasionally involved .

Studies has indicated the role of several risk factors such as genetics, sunlight, age, gender, hormones, pregnancy, thyroid dysfunction, cosmetics and medications .

Histologic features of melasma include an increase in the content of both epidermal and dermal melanin, but the quantity varies with the intensity of hyperpigmentation. In addition, most studies show no quantitative increase in melanocytes; however, the cells are enlarged with prominent and elongated dendrites and more abundant melanosomes. Additional features of the involved skin include solar elastosis and increased mast cells, dermal blood vessels, and expression of vascular endothelial growth factor.

Commonly used topical agents for the treatment of melasma include hydroquinone, azelaic acid, kojic acid, glycolic acid, salicylic acid and tretinoin. Of these treatments, hydroquinone remains the gold standard .Second-line treatments, such as chemical peels and lasers, are efficacious in some patients .

Chemical peeling is the application of a chemical agent to the skin, which causes the controlled destruction of a part or of the entire epidermis with or without the dermis, leading to exfoliation and removal of superficial lesions, followed by regeneration of new epidermal and dermal tissues [khunger, 2008]. The mechanism of action in melasma is the removal of unwanted melanin via controlled chemical burn of the skin .

Trichloroacetic acid has been used as a peeling agent for a long time and is still the most effective and safest agent for medium peeling, Its depth of penetration depends on the TCA concentration and on the preparation of the skin, specially the degreasing. Between 10% and 30% concentration is considered a superficial peel; above 30% provides a medium-depth peel.

Cryopeeling is a technique that uses cryotherapy in a diffuse manner throughout the skin region affected by sun damage in order to promote cell renewal and desquamation, with possible benefits in the appearance of new lesions caused by photodamage. Up to the investigator's knowledge, few studies were performed evaluating such technique.

Recently, trans-4-(Aminomethyl) cyclohexanecarboxylic acid, or tranexamic acid (TA), has been proposed as a new treatment for melasma.The main mechanism of the hypopigmentant effects of TA is due to its antiplasmin activity .In addition, TA is similar to tyrosine in a portion of its structure, which can inhibit tyrosinase competitively .Also, Plasmin transforms the vascular endothelial growth factor (VEGF) into a diffusing form, and histological examination showed that TA plays an important role in the reduction of erythema and vascularities and the number of mast cell in the dermis.Various forms of TA are used orally, topically and as a microinjection for the treatment of melasma.

Inclusion Criteria:

• -Subjects presented with melasma.
• Age 20-40 years old.
• Melasma persisting for more than 6 months that has failed to respond to conventional treatment with hydroquinone or other topical lightening agents.

Exclusion Criteria:

• -History of photosensitivity, keloids, hypertrophic scarring and post- inflammatory hyperpigmentation.
• Pregnancy and lactation.
• Subjects with local inflammatory skin disorder or active herpes infection at the site of procedure.
• Subjects with history of medical diseases which contraindicate cryosurgery such as; cold intolerance, cold urticaria, Raynaud's disease and history of allergic reactions to cryosurgery.