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Introduction:The relationship between allergic contact dermatitis (ACD) and atopy or atopic dermatitis (AD) is complex and incompletely understood.Objectives: To present an overview on possible interactions between ACD and atopy/AD, the value of patch testing in patients with AD and the impact of immunomodulatory AD treatments.Methods: Literature search on the relationship between ACD and atopy/AD.Results: ACD and AD share inflammatory pathways and clinical presentations and may coexist.Most epidemiological studies show no significant difference in prevalence of contact sensitization between patients with and without AD.Sensitizations to certain haptens/ allergens (e.g., fragrances, metals, and lanolin alcohol) seem to be more frequent in patients with AD which might partially be explained by a higher exposure to topical medications and moisturisers, but could also be related to a higher rate of false positive reactions.Recent studies indicate that not only Th1-, but also Th2-, Th17-and Th22-mediated immune responses are involved in ACD which may, however, depend on the causative hapten/allergen.Hence, systemic immunomodulatory AD treatments which inhibit Th2-mediated inflammatory pathways (e.g., dupilumab) may interfere with patch testing.However, several studies and case reports underline the usefulness to perform patch testing to exclude ACD in patients with AD even if they undergo immunomodulatory treatments.Conclusions: Patch testing is a useful investigation in AD patients as contact sensitizations and ACD are not uncommon in these patients.