A randomized, observer-blinded, crossover trial investigated the use of 5-methoxypsoralen (1.2 mg/kg, 2 h pre-UVA irradiation) with UVA (mean 21 mW/cm2) (PUVA) versus UVA1 (80-85 mW/cm2) in the treatment of 40 severe atopic dermatitis (AD) patients. The primary outcome measure was the length of remission after each treatment. The median length of remission was 4 and 12 weeks after UVA1 and PUVA, respectively (P = 0.012). Thus PUVA provides a better and long-term response than medium dose UVA1 in patients with severe AD (Tzaneva, S. et al. Br J Dermatol 2010, 162(3): 655).