Melasma is a chronic and relapsing acquired dyschromia due to an increased epidermal-melanin unit activity that affects sun-exposed areas mainly in women throughout the reproductive years. It is more common in women, accounting for 90% of all cases.The majority of patients are in third and fourth decades of their life. There are several risk factors that influence its appearance including genetic predisposition,exposure to heat and UV radiation, pregnancy, and exogenous hormones (such as oral contraceptives,thyroid hormones, and hormone replacement therapy). Other factors implicated are phototoxic drugs, anticonvulsant medications,and the use of certain cosmetics. Types of melasma are epidermal, dermal and mixed according to location of melanin.

Its pathogenesis is not fully understood, nevertheless there is evidence that melanogenesis in melasma differ from tanning and post-inflammatory hyperpigmentations as well as there is an involvement of the whole epidermal melanin unit in the process (not just hypertrophic melanocytes), mastocytes, fibroblast and endothelium derived cytokines, as well as there are upper dermal abnormalities different from other acquired pigmentary disorders. Patients with melasma have also been found to have higher markers of oxidative stress status.

Melasma has significant impact on patients physical health, interpersonal relationships ,social-well being and self- esteem as they refused to leave their house, felt inferior to others, and incessantly thought about their melasma being.

Melasma is often resistant to treatment and frustrating for both patients and clinician. In spite of presence of several methods for treatment of melasma exacted as, Topical compounds that include the Kligman's formula which is the triple combination of ( retinoid, hydroquinone, and steroid) and azelaic. Chemical peels (e.g., glycolic, β hydroxyl, and trichloroacetic acid )although these must be used cautiously in patients with darker skin. Laser and Light therapies represent potentially promising options for patients who are refractory to other modalities, but they also carry significant risk of worsening the disease.

Recently, some reports refer to the use of metformin in treatment of melasma. Metformin is antidiabetic drugs that was shown to exert its biological effect by decreasing cyclic adenosine phosphate , which is a well known modulator of melanin synthesis. Metformin decreased skin pigmentation in vivo with minimal side effects, suggesting a potential application of metformin in the treatment of hyperpigmentation disorders. Where the metformin was applied topically onto a mouse tail, whitening of the tail was observed. In addition, metformin decreased the epidermal level of melanin when metformin was applied to human skin punch biopsies and to reconstructed human epidermis. When melanocytes were treated with metformin, basal level of total melanin (eumelanin and pheomelanin) were reduced significantly. Also metformin blocked forskolin and alpha melanocyte-stimulating hormone which increase the levels of melanin. Metformin decrease levels of tyrosinase, tyrosinase-related protein-1 and tyrosinase-related protein-2.

Inclusion Criteria:

1. All patients above 18 years old with melasma.
2. With Fitzpatrick skin phototypes ranging from Type III-V will recruited.

Exclusion Criteria:

1. Pregnant or nursing women.
2. Current use of hormonal birth control medication or any hormonal therapy, Use of topical hydroquinone within 3 months of study, Use of topical steroids within 1 month of study, Regular use of tanning parlors and History of laser or dermabrasion to the face within 9 months of study.
3. Occupation involving primarily outdoor activities.
4. History of kidney dysfunction diabetic (excluded by history and laboratory), Significant cardiovascular or respiratory disease and any other systemic diseases(i.e,history of endocrine disorders).
5. patients with poor wound healing, recurrent herpes labialis and current skin infection (facial warts, molluscum contagiosum, history of hypertrophic scar/keloids, active dermatosis of atopic, seborrheic or other eczematous type).
6. Photosensitivity,