Background: It has been generally believed that the four main causes of melasma are pregnancy, hormonal contraception, family history and sun exposure; however, there are few published comprehensive studies that confirm these assertions. The Pigmentary Disorders Academy - an international group of experts in pigmentary disorders - designed and conducted a global survey of women to investigate the effect of these factors on onset and chronicity of melasma and the course of the disease in order to gain a better understanding of the causative factors associated with this disorder, with a particular focus on hormonal factors and UV exposure in females.

Methods: A 40-item largely self-administered questionnaire was completed by 324 women being treated for melasma in nine clinics worldwide.

Results: The mean age at onset of melasma was 34 years, and 48% of subjects questioned had a family history of melasma (97% in a first-degree relative). Subjects with family history of melasma tended to have darker skin (90% types III-VI) compared to those without (77% types III-VI). The most common time of onset was after pregnancy (42%), often years after the last pregnancy, with 29% appearing pre-pregnancy and 26% during pregnancy. Onset was related to darker skin type post-pregnancy (P = 0.002). Risk of onset during pregnancy was associated with having spent more time outdoors (an extra 10 h per week spent working outside increases the odds of onset of melasma during pregnancy by approximately 27%) and an increased maternal age at pregnancy (increased by approximately 8% for each year of age at first pregnancy; P = 0.02). The odds of melasma occurring for the first time during a pregnancy were also increased with multiple pregnancies (twice the odds if 2 vs. 1 pregnancies, three times higher if 3 or more vs. 1 pregnancy). Of the women, 25% who had used hormonal contraception claimed that melasma appeared for the first time after its use, the rate being higher for those without vs. with a family history.

Conclusions: The results suggest that, whilst accepted causes do affect onset of melasma, a combination of these factors often triggers this disorder. These factors may provide further insights into how physicians can manage individual melasma cases, support recommendation of preventative measures and even anticipate treatment results and recurrence.