There are several causes of hyperpigmentation depending on the type. The most common cause of hyperpigmentation is prolonged exposure to the sun, which triggers the body to produce more melanin as a form of protection. This over-production of melanin causes dark spots or patches on the skin also called age spots or sun spots. After an episode of inflammation from acne, eczema, lupus or an injury to the skin, areas of the skin can also darken and this is often referred to as post-inflammatory hyperpigmentation (PIH).
Other causes include genetic predisposition, hormonal changes such as pregnancy, reactions to certain medications (anti-malarial drugs, phototoxic drugs, anti-seizure and tricyclic antidepressants), chemicals in topical treatments.
Medical conditions such as Addison’s disease and hemochromatosis can also cause hyperpigmentation in certain areas of the body, including lips, knuckles, toes and insides of the cheek.