Background
Overwhelming evidence supports a causal relationship between occurrence of asthma and atopic dermatitis (AD).

Objective
The aims of the study were to determine the incidence of asthma in children with AD and to examine the health care utilization and drug use for asthma in children with AD.

Methods
Children with hospital-diagnosed AD (cases) were matched with individuals from the background population (controls) in a 1:4 ratio.

Results
In the final cohort (18,625 cases and 74,500 controls), the incident cases of asthma were 4203 among AD cases and 5298 in controls, corresponding to incidence rates of 34 and 9 in cases and controls per 1000 person-years, respectively (hazard ratio [HR] = 3.82, 95% confidence interval [CI] = 3.65–4.00). During the 1-year follow-up period from asthma diagnosis, children with concomitant AD had a significantly higher risk of hospital admission (HR = 1.97, 95% CI = 1.63–2.37), emergency department visits (HR = 1.62, 95% CI = 1.22–2.14), outpatient visits (HR = 1.97, 95% CI = 1.74–2.23), asthma medication (HR = 1.31, 95% CI = 1.27–1.35), and rescue course corticosteroids (HR = 1.74, 95% CI = 1.13–2.69) compared with children with asthma only.

Conclusions
The risk of being diagnosed with asthma was higher in children with AD. Risk of health care utilization and drug use for asthma was higher in children with both AD and asthma compared with asthma only.