Hyper-pigmentation are caused by varying concentrations of melanin; and some birthmarks by an unusual local proliferation of blood vessels (and hence of hemoglobin) near the skin surface. 

The darkening of skin by tanning results from an increase in melanin production under the stimulation of ultraviolet light. Hyper-pigmentation causes spots of darker skin to appear due to heavier deposits of melanin. Everyone is prone to such dark spots which are also sometimes called freckles. These spots or sometimes patches develop randomly on the skin and appear mostly near the eye area, cheeks, nose, arms, hands and neck.

From an aesthetic point of view, freckles, skin pigmentation and moles are often perceived as extremely undesirable. These dark spots and patches can be visibly reduced without having to undergo harsh and invasive treatment modalities.