Pigment protection factor as a predictor of skin photosensitivity--a Polish study

Assessment of individual photosensitivity by determining the minimal erythema dose (MED) is commonly accepted. MED objectively describes a single individual response to the irradiation of skin with a particular wavelength (UVB, UVA). Pigment protection factor (PPF) is an objective value to measure skin type. The aim of the project was to analyze PPF values in the population of Lodz and the relationship between PPF, skin phototype, and individual MED. The study was conducted on the group of 270 volunteers: 130 men and 140 women, mean age 28.5 years (OS + 9.66) with either skin phototype II or III, as defined by Fitzpatrick Skin Phototype Classification. Phototesting of each volunteer was undertaken with an increasing dose series (UVB radiation) on six squares (1×1 cm) on the skin of the back. The MED was defined as a perceptible erythema 24 hours later. Starting dose was determined by history, physical examination, and phototype ranged from 0.03-0.07 J/cm2. PPF was measured by a skin reflectance meter UV Optimize 555. The mean MED value was 0.15 J/cm2 and the PPF value was 6.15. A positive correlation between the MED value and PPF (R=0.38; P<0.001), and a positive correlation between phototype and MED and PPF (P< 0.001) were found. Both determination of MED and PPF are objective methods of photosensitivity assessment, but PPF determination is an easy and non-invasive method.