Contact allergy and allergic contact dermatitis to benzalkonium chloride in a tertiary dermatology centre in Melbourne, Australia.

Dear, Kate; Palmer, A; Nixon, R

BACKGROUND Benzalkonium chloride (BAK) is a quaternary ammonium compound widely used as an antiseptic and preservative. It is a strong irritant and considered a weak sensitiser. OBJECTIVE To analyse the temporal trend of BAK sensitisation and the demographics of sensitised patients. METHODS We conducted a single centre retrospective study of 7390 patients patch tested with BAK between 1 January 2003 and 31 December 2019. RESULTS Of 7390 patients patch tested to BAK, 108 (1.5%) had a positive reaction, with 21 reactions deemed clinically relevant (0.3% of total patch tested) and a further 5 doubtful reactions deemed clinically relevant resulting in a total of 26 relevant reactions (0.4% of total patch tested). Common sources of exposure were ophthalmic drops (30.8%), topical antiseptic preparations (26.9%), cosmetics (15.4%), disinfectant solutions (11.5%), hand sanitisers (11.5%), and hand washes (7.7%). One fifth of patients with relevant reactions were healthcare workers. There has been a dramatic increase in the number of positive reactions since 2017, for reasons not totally clear. CONCLUSION Contact allergy (CA) and allergic contact dermatitis (ACD) to BAK are now increasing at our centre. Awareness of this trend is important, given that the COVID-19 pandemic is likely to further expose people to BAK. This article is protected by copyright. All rights reserved.