AbstractBackgroundThe international classification of diseases, 10th revision (ICD‐10) includes several unvalidated diagnostic codes for hand eczema (HE). Knowledge is sparse on HE patient characteristics.ObjectivesTo validate selected HE ICD‐10 codes in the Danish National Patient Registry (DNPR) and describe disease characteristics, lifestyle factors and medication use in adult HE patients.MethodsNineteen HE ICD‐10 codes were selected and validated based on patient charts. Five cohorts were constructed based on the diagnostic code, DL30.8H (HE unspecified), in the DNPR: (i) patients with DL30.8H code (n = 8386), (ii) patients with DL30.8H code, but without atopic dermatitis (AD) (n = 7406), (iii) sex‐ and age‐matched general population (n = 8386) without HE. Two additional cohorts nested in the DNPR included participants from the Danish Skin Cohort, (iv) patients with DL30.8H code but without AD (n = 1340) and (v) general population cohort (n = 9876).ResultsICD‐10 codes revealed positive predictive values ≥90% except irritant contact dermatitis (unspecified) (79.7%) and hyperkeratotic hand and foot eczema (84.1%). HE patients were most often women, middle‐aged or older, of Danish ethnicity, had an atopic medical history and were smokers. Topical corticosteroid prescriptions were almost doubled in HE cohorts compared to general populations.ConclusionWe validated several HE ICD‐10 codes and identified important HE patient characteristics.