Photoallergic contact dermatitis caused by wooden catholic bracelets: A report of two cases

Background: Non-occupational cases of contact dermatitis to finished wood are occasionally reported from contact with wooden jewellery, musical instruments, knife handles and wooden footwear. Two female patients, 26 and 34 years old, developed acute eczema on the wrists after they worn in the summer a kind of catholic bracelet called “memorabilia” made by single wooden chunks with over-impressed iconic religious images. Objectives: To identify the culprit photoallergen responsible for the reported adverse reactions suspected to be a compound of the wooden bracelets. Methods: Three months after the resolution of the dermatitis, patch test and photo-patch tests were performed with the S.I.D.A.P.A. (Italian Society of Allergic, Occupational and Environmental Dermatology) standard series, and with wood sawdust obtained from both bracelets and tested at 5% in pet. A thin-layer chromatogram (TLC) strip and an extract made from the bracelets were tested in both the patients as patch test and photo-patch test. The extracts of the wooden bracelets were analyzed by gas chromatography – mass spectrometry (GC-MS). Results: Patch tests and photo-patch test with standard series turned out negative. Photo-patch tests with wood sawdust in pet. 5% evidenced a positive reaction (++) in both patients. Two chemicals were detected in the wooden bracelets with GC-MS: dibutylphthalate, commonly used as plasticizer, and 8,8-dimethyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-2-one, a coumarin. Patch test with TLC did not elicit positive reactions but the photo-patch test with TLC gave positive reactions in both the patients to the same invisible spot on the strips. Two coumarins (8,8-dimethyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-2-one and 8,8-dimethyl-2H,8H-benzo[1,2-b:5,4-b']dipyran-2-one) were detected in the spot with GC-MS. Conclusion: Coumarins are chemicals found in many plants with a known photo-allergic potential. They are probably the main photo-allergens in religious wooden bracelets instead of quinones and psoralens hypothesized in previous reports.