Allergic contact dermatitis (ACD) is characterised by type IV hypersensitivity to a specific allergen and is diagnosed by patch testing, where allergens are placed against the skin. The ‘baseline series’ refers to a set of the most important allergens used as a screening series and must be relevant to the population tested. In 2015, an Australian baseline series (ABS) was proposed based on a 10-year retrospective review of patch test results in Victoria. The primary objective of this work was to describe patch test results in patients undergoing testing at The Skin Hospitals in Darlinghurst and Westmead in New South Wales.
Data was retrospectively collected from The Skin Hospital’s Microsoft Access database from 1 January 2002 to 31 December 2016. Information collected included demographic details, clinical presentation and patch test results. The most recent ten-year period was used for most analyses to provide results with current relevance.
In the last-ten-years 1,584 patients were patch-tested at The Skin Hospitals in NSW. The positivity rate (proportion of patients with ≥ 1 positive reaction) was 27.8%. The most frequently positive allergens were nickel sulfate, cobalt chloride, Myroxylon pereirae (balsam of Peru), fragrance mix I and p-phenylenediamine (PPD). Rates of positivity to metals, methylchloroisothiazolinone/methylisothiazolinone, PPD, colophonium and Myroxylon pereirae increased in 2012-2016 compared with 2007-2011. The ABS detected 71.5% of positive reactions and 72.9% of relevant reactions.
Our study had an overall lower positivity rate and lower rates of occupational and hand dermatitis compared with data from Victoria and therefore provides useful information on the performance of the ABS in a general patch-testing clinic. Top allergens were in keeping with other Australian and International reports, with the possible exception of dodecyl gallate, which had more positive and relevant reactions than expected. The rise in nickel sensitisation, converse to some International reports, warrants ongoing surveillance as there is no current Australian legislation to regulate nickel in products contacting the skin.