Long-lasting pigmentation more than its intensity is a reliable indicator of skin sun resistance

BACKGROUND: The currently adopted method for predicting sun sensitivity is Fitzpatrick's classification which however is based on self-reported burning tendency and tanning ability. Objective: Determination of the individual UV susceptibility based on non-subjective parameters. METHOD: Minimal erythema dose (MED), intensity and duration of pigmentation on days 5, 9 and 16 following 1 MED and the levels of the melanin marker pyrrole-2,3,5-tricarboxylic acid (PTCA) were analysed in non-red-haired subjects (50, aged 20-46 years). RESULTS: Phenotype groups or phototypes showed a good correlation with PTCA yields and the persistence of pigmentation on day 16, but not with MED values. MED values did not show a significant correlation with PTCA yields. On the other hand, high values on day 16 were exhibited only by subjects having PTCA values higher than 200 ng/mg. CONCLUSIONS: Measurement persistence of pigmentation on day 16 represents a non-invasive and easy-to-perform method to evaluate photoprotection in those individuals escaping straightforward classification based on phenotype or anamnesis.