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History of photopatch testing
Department of Dermatology, Allergology and Environmental Medicine HELIOS Klinikum Wuppertal, University of Witten-Herdecke, Germany
Photoallergic reactions were observed for the first time after the introduction of sufonamides in the 1930s. Somewhat later, phenothiazines gained interest as photosensitizers. In order to accomplish a correct diagnosis and to detect the causative agent first attempts to perform photopatch testing were undertaken in the late 1930s. Stephen Epstein was the first researcher, who described in detail the methodology of photopatch testing in 1939. In Germany, K.S. Schulz performed extensive studies employing photopatch testing in order to evaluate the photosensitivity of phenothiazines. During the years from 1962 to 1970, halogenated salicylanilides were identified as the cause of widespread outbreaks of photoallergy. The photosensitivity was traced down to the use of deodorant soaps and cosmetics containing salicylanilides as antimicrobial agents. Since then, the photopatch test has been adopted in clinical dermatology as the gold standard of investigation to identify photoallergens. However, until the early 1980s, photopatch testing was not standardized. The procedure varied between dermatology centres, among different countries and internationally, as has been shown by a worldwide survey.
The first attempt to standardize the method was initiated by the Scandinavian Photodermatitis Research Group (SPDRG) in 1982. Stimulated by the result of the above mentioned international survey, and following the example of the SPDRG, 45 dermatology hospitals in Germany, Austria, and Switzerland joined in 1984 to a Photopatch Test Group in order to perform an epidemiological study on photoallergens, and also to finally standardize the procedure. The first report of this large group appeared after an evaluation after 5 years, and consecutively the final results after 12 years. In both test periods, nonsteroidal anti-inflammatory drugs, disinfectants, and phenothiazines represented the leading photoallergens in the evaluated central European region. Sunscreens were the most frequent photoallergen relevant to the investigated clinical picture. By using computer assisted reaction-pattern analysis, substance specific reaction patterns could be distinguished. Test modifications after the first period led to a remarkably improved specificity of the procedure.
Following this example, a multicentre photopatch study group was established in the U.K. with similar aims. Here, sunscreens were detected as the most frequent photoallergens, not only causing photosensitivity but also contact sensitivity. Large photopatch test sudies were also reported from New York (monocenter study), and Italy (multicenter study). These efforts led finally to the initiation of a European Photopatch Test study group. The participants are currently investigating photosensitivity caused by photoallergens throughout Europe following a consensus methodology.
© Percy Lehmann (text) and Radoslaw Spiewak (source code).
This page is part of the website photopatch.eu (contact).
Document created: 30 August 2009, last updated: 31 August 2009.