Coexistence of allergic diseases: patterns and frequencies.

The atopic march hypothesis suggests that allergy diseases often progress from atopic dermatitis to allergic asthma, and allergic rhinitis. How often can the classic progression of allergic diseases be observed in the pediatric patient population? This study aimed to observe the pattern of allergic diseases progression, onset age, disease intervals, and frequency of the allergic march. Data from the National Health Insurance Research Database in the period 1996-2008 were used to obtain a cohort of children with allergic disease. Physician's diagnosis was used to confirm the allergic disease based on the international disease coding. The age of disease onset was compared. There were 10,729 children aged <5 years enrolled from the 200,000 individuals randomly sampled in 2000. Of these, 5866 (54.7%) had been diagnosed with at least one allergic disease. The rate of only one of three diseases diagnosed was 29.8% (3195 patients), whereas 18.8% had two allergic diseases and 6.1% had all three allergic diseases. Only 4.2% of cases matched the allergic march. Patients with more than one disease had earlier onset age than those who had only one disease (4.17 versus 2.79 and 2.32 years old; p < 0.05). The allergic march accounts for only 4.2% in this study. A patient with only one allergic disease after the age of 4.17 years will not have another allergic disease until the age of 12 years. However, a patient with an allergic disease before 2.79 years old will probably have another allergic disease in 1.96-2.5 years.