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The epidemiology of photoallergy
Photobiology Unit, Ninewells Hospital, Dundee DD1 9SY, Scotland, UK
Photoallergy is investigated by photopatch testing, but due to the multiple steps involved, methodology can vary greatly. Over the past 3 decades, groups have attempted to standardise photopatch testing methodology within different European countries. Recently, a European consensus methodology has been published to further aid standardisation and facilitate accurate comparison of results between centres . The precise incidence of photoallergy is not known. Results from a U.K.-wide multicentre study of organic sunscreen filters demonstrated a frequency of 4% for photocontact allergy alone and 5% for contact allergy alone. This study also emphasised the importance of testing the patients own products .
Presently, a European multicentre photopatch test study is underway to determine the frequency of photoallergy to 19 organic sunscreen filters and 5 topical nonsteroidal anti-inflammatory drugs (NSAIDs). In preparation for this, a pilot study was conducted in one U.K. centre investigating the irritant potential of the 19 sunscreen filters used in the present Europe-wide study. This demonstrated that 18 filters could be used at concentration of 10% for photopatch testing and one, benzophenone-4, should be used at a concentration of 2%, due to its higher irritant potential.
An interim analysis of the results of the present European study has shown that 2 NSAIDs, ketoprofen and etofenamate, appear to produce a high frequency of photoallergy. Although leading to fewer reactions than these 2 NSAIDs, the organic sunscreens octocrylene and benzophenone-3 appear to cause more photoallergic reactions than other sunscreens. The importance of testing the patients’ own products is again evident, with high numbers of reactions to proprietary preparations. Similar to previous studies, the number of reactions showing photoaugmentation and photoinhibition of contact allergy remains low. However, contact allergy alone to agents remains important in numerical and clinical terms.
© Alastair Kerr (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.