Pigmentation is the term most often used to describe dark marks or patches on the skin-In particular the facial skin. However, strictly speaking disorders of pigmentation can be divided into conditions resulting in hypopigmentation (lightening of the skin) and those resulting in hyperpigmentation (darkening of the skin).

The best known disorders of hypopigmentation are vitiligo and albinism. Disorders of hyperpigmentation(increased pigmentation) can be widespread or localised.

Causes include genetic disease, metabolic abnormalities (thyroid, liver, renal and endocrine diseases), vitamin and nutritional deficiencies. These patients could have other symptoms or signs of the underlying problem. Certain medication may cause hyperpigmentation as an adverse drug reaction.
Melasma and and post inflammatory hyperpigmentation (PIH) are by far the commonest and most distressing forms of hyperpigmentation seen by dermatologists.