C.WEE1, C.H.TAN2, X.H.ZHAO2, Y.W.YEW2, A.GOON2
MOH Holdings Pte Ltd (MOHH)1, National Skin Centre2
The pathogenesis of atopic dermatitis and allergic contact dermatitis share similar immunologic pathways. Although the traditional understanding is that contact sensitisation is less frequent in patients with atopic dermatitis, recent studies have shown similar or higher rates of positive patch test results in patients with atopic dermatitis. Such studies are presently lacking in Asia.
This was a single-centre, ten-year retrospective review on contact sensitisation in patients who underwent patch testing between 2007 and 2017 in the National Skin Centre, Singapore. The aims of the study were to characterise the pattern of contact sensitisation in our local population and to ascertain a link between contact sensitisation and atopic dermatitis.
There were 4904 patients (males:females = 1:1.39; mean age 40.1 years old) included in the study, of whom 2530 (51.6%) had been previously diagnosed with atopic dermatitis. About half (2499, 51.0%) of all patients developed at least one positive reaction. The top five frequent reactions were to nickel sulfate (45%), potassium dichromate (16%), p-phenylenediamine (13%), balsam of Peru (12%) and fragrance mix I (11%). The overall prevalence of contact sensitisation, defined as at least one positive patch test result, was not significantly different between patients with or without atopic dermatitis. Contact allergies to budesonide or thiuram mix was less likely to arise in patients with atopic dermatitis.
Contact sensitisation was detected in 50% of patients patch-tested. Nickel sulfate was the most frequently sensitising allergen. The prevalence of contact allergies in atopic patients is comparable to that in non-atopic patients.