The contribution of filaggrin null mutations to predicting atopic dermatitis (AD) treatment response is not clear, nor have such mutations been studied in the Finnish population. This study tested the association of the 4 most prevalent European FLG null mutations, the 2 Finnish enriched FLG null mutations, the FLG 12-repeat allele, and 50 additional epidermal barrier gene variants, with risk of AD, disease severity, clinical features, risk of other atopic diseases, age of onset, and treatment response in 501 patients with AD and 1,710 controls. AD, early-onset AD, palmar hyperlinearity, and asthma showed significant associations with the combined FLG null genotype. Disease severity and treatment response were independent of patient FLG status. Carrier frequencies of R501X, 2282del4, and S3247X were notably lower in Finns compared with reported frequencies in other populations. This data confirms FLG mutations as risk factors for AD in Finns, but also questions their feasibility as biomarkers in predicting treatment response.