S.Y.D.LIM1, T.J.A.GOON1, Y.H.LEOW1, W.N.S.CHENG1
National Skin Centre1
Patch testing to a standard series, comprising the commonest and most important offending contact allergens, is an important screening tool for patients with suspected allergic contact dermatitis. We aim to identify the frequency distribution and temporal trends of contact allergens in the standard series at our tertiary referral center over a six-year period from 2014 to 2019.
Patients with suspected contact dermatitis were patch tested to the modified European standard series, and results were analyzed.
A total of 2370 patients underwent patch testing, of which 1171 (49.4%) had a reaction to one or more allergens. The mean age was 47.0 years. 874 (36.9%) patients were male. The top ten allergens in order of frequency were nickel (II) sulfate hexahydrate (23.4%), potassium dichromate (9.32%), p-phenylenediamine (7.43%), colophony (6.50%), fragrance mix 1 (6.50%), balsam of Peru (6.33%), fragrance mix 2 (3.54%), neomycin sulfate (2.62%), paraben mix (2.53%), and thiuram mix (1.94%). 331 of 1874 (17.7%) positive patch test results became positive only at day 7.
Compared to previous local epidemiologic data from 2009 to 2013, nickel remains the top allergen. The prevalence of potassium dichromate sensitization doubled from 4.62% to 9.32% (p < 0.000001), mirroring a slight increase noted in Central Europe and Australia. Rising consumption of leather products and occupational exposure to cement may be responsible. Smaller increases were noted for Balsam of Peru and paraben mix. Changes in prevalence of contact allergy reflect evolving societal and industrial practices, and continued temporal evaluation identifies areas of public health significance.