5-S-cysteinyldopa and pigment response to UVA light

5-S-Cysteinyldopa concentrations in serum were studied in healthy individuals exposed to daily high-intensity UVA radiation. A marked increase in 5-S-cysteinyldopa was found after 3 days, and in some individuals concentrations were still higher after 7 to 10 days. The immediate pigment darkening (IPD) and delayed tanning (DT) were weak or absent at pressure sites, i.e. in skin with a low concentration of oxygen.