Twenty five studies were included in the review (n=454, range three to 80). Five studies were randomised controlled trials. The other studies were either open-label, uncontrolled studies or retrospective case reports.
Within studies that dealt with the application of beta-carotene (16 studies; n=337), 54% of patients reported a strong improvement in in EPP symptoms, 28% reported moderate improvement and 18% no improvement. Reactivity in phototesting (two studies) yielded a strong effect in 15% of patients, moderate effect for 56% and no effect in 29%. Four of the five well-designed studies suggested lack of efficacy of beta-carotene; efficacy was inversely correlated with study quality.
Results for additional interventions were reported, but not synthesised.