Melanocytes are cells within the skin that produce pigment color (melanin). They inject this color into other cells that move upwards toward the skin surface. Think dark spots and suntans. Ideally this pigment will be a smooth, even coloration.
When there is too much color injected into one area, the appearance becomes blotchy and uneven. This is referred to as hyper-pigmentation and is a tell-tale sign of aging and internal imbalances.
Dark colors absorb light rays, and dark skin absorbs more light. When melanin makes the skin darker, it buffers and interacts with U.V.radiation to protect the deeper body tissues; the body deposits melanin where there is a lot of electrical activity (the brain and eyes in addition to the skin are sites of melanin accumulation)
While exfoliating and melanin suppressing treatments (e.g. alpha hydroxy acids and hydroquinone) can eliminate pigment, the underlying condition that causes it in the first place is under hormonal control and can only be addressed effectively through internal strategies. Nutritional supplementation with anti oxidants can help. Vitamin C and E are particularly effective anti hyper-pigmenting agents. Essential fatty acids may be helpful as well. And not just taken orally. According to a 1998 article published in the Archives of Dermatological Research topically applied Omega 6 and Omega 3 fatty acids can induce a decline in hyperpigmentation after 3 weeks of treatment.