Health care costs of allergic rhinitis-associated conditions vary with allergy season.

Background: Studies have documented how allergic respiratory symptoms vary with allergen levels, but the impact of allergen levels on health care expenditures for allergy-related conditions has never been shown using actual data on outdoor allergen levels. Evidence linking respiratory allergy to comorbid conditions has also been scanty.
Objective: To investigate the link between respiratory allergy and presumably associated conditions by documenting seasonal patterns in their severity and co-occurrence, and to suggest a plan for future research.
Methods: A retrospective, cross-sectional analysis of medical claims data from 1995 to 1996 were linked to monthly data from federal counting stations on outdoor allergen levels. Participants were employed persons and their dependents, living within 15 miles of an allergen-counting station, continuously enrolled in a health plan for 1995 and 1996, and identified through medical claims data as having asthma, allergic rhinitis (AR), migraines, sinusitis, tonsillitis, otitis media, depression, or anxiety disorder.
Results: All conditions studied were more likely to occur during allergy season than during nonallergy season. For persons with health care claims for a condition of interest in both seasons, total health care costs during allergy season were significantly higher than during nonallergy season. Predicted condition-related expenditures were higher in allergy season for every condition even after controlling for the effect of AR.
Conclusion: Allergy effects appear to extend beyond AR symptoms. Other conditions may be affected by outdoor allergen levels even in the absence of AR symptoms, implying that these conditions may be etiologically related to allergy, irrespective of their co-existence with allergic rhinitis, further implying that allergic sensitization can independently affect different parts of the respiratory tract as well as the brain.