Patch test results in patients with suspected allergic contact dermatitis: a study from Mashhad, Iran and a review of literature

Background: The standard patch test is known as the most reliable test to identify and confirm causative agents of allergic contact dermatitis (ACD). Previous studies have shown that the prevalence of specific allergens varies by geographic area. The results of patch test in patients visiting our dermatology clinics with suspected ACD were prospectively investigated and compared with those reported in the literature of Iran. Method: We performed the European Standard Series patch test produced by Almiral Hermal GmbH, containing 28 allergens in a group of 100 patients (55 females and 45 males) with suspected ACD who were referred to Emam Reza and Ghaem Hospitals, Mashhad, in 2010-2011. The tests were read after 2 and 4 days. Result: Fifty-four percent of the patients had 1 or more positive reactions of which 65% were relevant to current or past dermatitis. Positive reactions were due to 12 allergens. The most frequent allergens were nickel sulfate (25%) and potassium dichromate (25%), followed by cobalt chloride (15%), thiuram mix (11%), para tertiary butylphenol formaldehyde resin (5%), fragrance mix II (3%), para-phenylenediamine free base (3%), colophony (1%), wood alcohols (1%), mercapto mix (1%), budesonide (1%), and sequiterpene lactone mix (1%). The positive reaction to nickel was significantly more common in women (p<0.001). Men showed significantly more positive reactions to chrome (p<0.001). According to the localization of ACD, hands, as the most common site, were involved in 59 (59%) cases, followed by the feet in 28 (28%) cases. Conclusion: Nickel sulfate and potassium dichromate are the most common allergens in Iran. As the causative agents of contact dermatitis are different in various geographic areas, modifying standard patch test series in each region with regard to its allergen prevalence might be a reasonable and cost effective approach for more appropriate preventive measures and therapeutic strategies.