Not All Itch Is Created Equal in Atopic Dermatitis: A Prospective Observational Study of the Heterogeneous Characteristics of Itch

<u><b><i></i></b></u> <u><b><i>Background:</i></b></u> Although itch is the universal symptom of atopic dermatitis (AD), little is known about its clinical phenotypes in AD.<u><b><i>Objective:</i></b></u> To examine the relationships of itch characteristics and patterns with AD severity, mental health, sleep, and quality of life (QOL).<u><b><i>Methods:</i></b></u> We conducted a prospective study of 456 adult patients with AD using validated questionnaires and skin examinations. Thirteen itch characteristics were assessed with the Patient-Reported Outcomes Measurement Information System Itch-Quality. Multivariable regression models evaluated the associations of itch characteristics, severity, or patterns with outcomes.<u><b><i>Results:</i></b></u> A total of 283 (62%) patients described their itch with ≥1 descriptor-most commonly, stinging (29%), tingling (24%), burning (23%), and painful (23%). The number of itch characteristics reported and endorsement of at least one itch quality were associated with greater AD and itch severity, history of anxiety and depression, active symptoms of clinical depression, sleep impairment, and QOL decrement. Reporting ≥1 itch characteristic remained associated with anxiety, active depression, sleep disturbance, and QOL impact independent of itch severity. All 13 itch descriptors were associated with worse sleep and QOL even after controlling for itch severity. Dermatitis affecting the face, eyelids, hands, or feet was each associated with distinct patterns of itch qualities. Latent class analysis identified three phenotypes of itch, which correlated with AD and itch severity, active symptoms of depression, and QOL decrement.<u><b><i>Conclusion:</i></b></u> Adults with AD commonly describe their itch heterogeneously using pain-related sensory descriptors. The quality of itch may independently predict mental health outcomes, sleep impairment, and QOL impact.