Melasma is the most common cause of facial hyperpigmentation and is characterised by symmetrical, blotchy, brownish pigmentation that becomes more pronounced after sun exposure.
- The pigmentation is caused by the overproduction of melanin, which is taken up by the keratinocytes (epidermal melanosis) and/or deposited in the dermis (dermal melanosis)
- The exact cause is unknown
- There is a genetic predisposition with at least one-third of patients reporting other family members to be affected
- The most important exacerbating factor is UV radiation. Other factors include pregnancy, and the combined oral contraceptive pill. In the context of pregnancy, melasma is regarded as a normal physiological change, along with darkening of the nipples and linea nigra
- The rarity of melasma in postmenopausal women on oestrogen‐containing hormone replacement therapy and the fact that men are occasionally affected suggests that oestrogen alone is not the causative agent