Contact Dermatitis

Background: Severe contact dermatitis is a cause of hospitalisations.Paraphenylenediamine (PPD), such as in hair dyes, is one commonly implicated contact allergen.Aims: To assess the burden on emergency and inpatient services from allergic contact dermatitis secondary to PPD, and whether intervention with patch testing may reduce hospitalisations.Methods: A retrospective analysis was performed of patient records at a tertiary dermatology centre.Patients who tested positive for PPD had their records reviewed for all hospital presentations occurring before or after the patch test date.Presentations to the emergency department and admissions secondary to 'rash', 'allergy', 'eczema' or other conditions thought to be related to hair dye or PPD allergy were included.Results: A total of 956 patients underwent patch testing between July 2008 and September 2023.A total of 48 patients tested positive for PPD allergy on patch test (female n = 33 (67%); age range 18-72 years (mean 53 years)).The post-patch test diagnosis was allergic contact dermatitis in 29 patients (60%).The largest single ethnic group was Indian (n = 12 (24%)), followed by European (n = 11 (24%)) and Maori (n = 10 (20%)).Of these patients, 18 (37.5%)had at least one hospitalisation and nine (50%) had presentations to hospital after their patch test.The reasons for repeat hospitalisation after patch test included nonadherence to allergen avoidance advice and exacerbation of comorbid dermatoses.Conclusion: PPD allergies presenting as allergic contact dermatitis other dermatoses are a significant cause of hospital presentations and inpatient admissions.Patch testing reduces the rate of re-presentation in some patients.