Melasma tends to occur in people with a more olive or darker skin. Hormonal factors such as pregnancy and taking a contraceptive pill containing estrogen can trigger this condition.
The slightest sun exposure can produce melasma which is brown pigmentation often over the forehead and cheeks. That is why it is vitally important to use a high-factor broad spectrum sunscreen when heading outdoors.
In the initial stages, the pigmentation is sitting superficially in the epidermis (top layer of the skin) and the melasma is relatively easy to treat, often with sun avoidance, high factor, broad spectrum sunscreen and the appropriate use of non-hydroquinone products are used to target this condition.
The longer that the melasma is present, the more difficult it is to treat as the pigment falls from the epidermis (top layer) into the dermis (deeper layer) where it is more difficult to completely clear with non-prescription topical products.
At this stage, it would be advisable to consult a Dermatologist or a doctor with experience with pigmentation.