There are several causes of hyperpigmentation depending on the type. The most common cause is prolonged sun exposure, which signals the body to produce more melanin as a protective response. This overproduction leaves dark spots or patches often described as age spots or sun spots. After inflammation from acne, eczema, lupus or an injury, the affected skin can also darken. This is known as post-inflammatory hyperpigmentation, or PIH.
Other causes include genetic predisposition, hormonal changes such as pregnancy, reactions to certain medications (antimalarial drugs, phototoxic drugs, anti-seizure medications and tricyclic antidepressants), and chemicals in topical treatments. Medical conditions such as Addison’s disease and haemochromatosis can also cause darkening in specific areas, including the lips, knuckles, toes and the inside of the cheek.
What happens if pigmentation is left alone? Many forms of hyperpigmentation are benign, and some forms such as PIH may fade gradually over time. However, ongoing UV exposure or continued inflammation may contribute to persistent or worsening pigmentation. Consistent daily sun protection is an important preventive measure.