Measurement of Constitutive Skin Phototypes

Abstract

Skin phototypes are in this study defined as the number of standard erythema doses (SED) that are needed to elicit just perceptible erythema on previously UV unexposed skin. In the majority of persons the test site may be found on the buttocks. This measure is almost constant throughout the year and throughout life and is, therefore, suitable for use in epidemiologic studies of skin cancer and other UV related skin conditions. This is in contrast to the situations when the UV dose to be used in phototherapy is established, where UV exposed sites such as the arm or the back are normally used.

The skin phototype is generally determined by a MED test. However, this test is insensitive for grading of UV sensitivity in fair-skinned Caucasians and the reproducibility is far less than generally expected. Other estimations of skin phototypes are build on questionnaires of anamnestic sun burn tendency and tanning ability and are easy to apply in population studies but are, however, unreliable. Other insensitive methods are build on race, includes eye colour and hair colour, or cards with colour and photos of different grades of skin pigmentation. The best method is offered by skin reflectance measurements of pigmentation on un-exposed buttock skin. Such measurements correlate well to MED phototest, have a high resolution in all races, measures non-invasively, and may be performed in a few seconds.