The combined diagnosis of allergic and irritant contact dermatitis in a retrospective cohort of 1000 consecutive patients with occupational contact dermatitis

BACKGROUND: The diagnosis of combined allergic and irritant contact dermatitis is an accepted subdiagnosis for hand dermatitis, and it is often considered in a patient with contact dermatitis, a positive and relevant patch test result, and wet work exposure. We therefore hypothesize that it is arbitrary for wet work exposure to be taken into consideration in a patient with newly diagnosed relevant contact allergy. Furthermore, an overestimation of the diagnosis will probably occur if the criteria for wet work exposure are applied correctly, as many occupations have an element of wet work. OBJECTIVES: To find the statistically expected number of combined allergic and irritant contact dermatitis cases in 1000 patients, and to evaluate the diagnostic criteria for the diagnosis. METHODS: One thousand consecutive patients with occupational contact dermatitis from a hospital unit in Denmark were assessed. RESULTS: The expected number of cases with the diagnosis of combined allergic and irritant contact dermatitis was 0.33%, as compared with the observed number of 6.4%. Females occupied in wet occupations were often diagnosed with combined allergic and irritant contact dermatitis (p < 0.005). CONCLUSION: The diagnosis of combined allergic and irritant contact dermatitis should be used critically to avoid misclassification, and possible criteria for the diagnosis are proposed.