Ultraviolet erythema sensitivity in anamnestic (I-IV) and phototested (1-4) Caucasian skin phototypes: the need for a new classification system

The anamnestic skin phototypes (ASP) I-IV of 22 Caucasian volunteers wee compared with their phototested skin phototypes (PSP) using solar simulating, broadband UV radiation. The Commission Internationale de l'Eclairage (CIE)-weighted (i.e. erythemally effective) minimal erythema doses (MED) for solar simulating radiation varied from 20 mJ/cm2 (PSP type 1) to 57 mJ/cm2 (PSP type 4). In only 11 of 21 volunteers did the ASP (I-IV) and PSP (1-4) classifications coincide, and the MED values of the volunteers within the different ASP groups (I-IV) overlapped considerably. To compare the reactivity to erythematogenic radiation of different wavelengths, narrowband monochromator irradiations were performed at 298 nm, 310 nm and 330 nm. The CIE-weighted MED values at these wavelengths (20-80 mJ/cm2) corresponded well with those obtained in the broadband testing. Our results indicate that, with classification by interrogation, Caucasian skin can reliably be classified into only two subtypes, corresponding to Fitzpatrick phototypes I-III and phototype IV, respectively. A classification into four sensitivity types can be achieved by phototesting, only. We propose that the concept of ASP should be used with caution. The concept of PSP 1-4 should be favored.