Allergic Contact Dermatitis in Atopic Individuals: Results of a 30‐year Retrospective Study

BACKGROUND: The association between atopic dermatitis (AD) and contact allergy, remains unclear, with studies to date showing conflicting results. OBJECTIVES: To investigate the prevalence of contact allergy in AD individuals compared to those without AD. METHODS: Results of 46 250 patients patch tested in a single centre over a span of 30 years were reviewed, comparing those with AD with those without AD. Collected data were analysed with corrections for multiple confounding variables, including date of patch testing to account for changes in allergens tested over the period. RESULTS: Nine allergens showed a statistically significant difference between the two groups. Contact allergy to nickel, cobalt and primin was less likely to arise in those with AD, whilst substances found in topical dermatological products were more likely to be associated with AD. CONCLUSIONS: This is the largest single centre study of contact sensitization in atopy reported to date. The previously reported association between contact allergy to sesquiterpene lactone and AD is reinforced. The decreased incidence of metal allergy suggests distinct immunological effector mechanisms in sensitization to these allergens. In keeping with previous publications, exposure to topical treatments for AD can result in sensitisation and contact allergy and clinicians should consider patch testing in AD individuals who report worsening of their skin despite continued treatment with topical medicaments.