BACKGROUND: To our knowledge, disease burden of atopic dermatitis (AD) as number of days with symptoms and medical treatment has never been studied as measure of severity.

OBJECTIVES: To investigate risk factors for AD burden in the first 3 years of life.

METHODS: The Copenhagen Prospective Studies on Asthma in Childhood2010 included 700 children. AD burden was assessed by daily diary entries with information on AD and steroid days measuring 18 possible heritable, prenatal, and postnatal environmental exposures.

RESULTS: The children with AD had a median (interquartile range) of 136 symptom days (61-294 days) and 72 steroid days (27-145 days) during the first 3 years of life, with the highest disease burden in the second year of life. The multivariable risk factor analysis showed that maternal AD and childhood allergic sensitization were associated with a higher number of AD days and maternal AD, filaggrin mutation, and allergic sensitization were associated with a higher number of steroid days.

LIMITATIONS: Participants with a personal interest in atopic diseases could be more likely to participate.

CONCLUSION: Children's burden of AD, assessed quantitatively as AD and steroid days, demonstrated positive associations with maternal AD, filaggrin mutation, and early-life allergic sensitization, with the highest disease burden in the second year of life.