Reduced levels of histidine and urocanic acid in suction blister fluids from patients with psoriasis.

: Metabolites of histidine were determined by high performance liquid chromatography in suction blister fluids from lesions and normal appearing skin of patients with psoriasis and from healthy subjects. There was a significant decrease in the levels of histidine and urocanic acid in the samples obtained from patients with psoriasis as compared to healthy subjects. Virtually only the E-isomer of urocanic acid was detected.