BACKGROUND: The atopic march is well documented, but the interrelationship of food allergy (FA) and asthma is not well understood. OBJECTIVE: The aim of this study was to examine the strength of the association and temporal relationships between FA and asthma. METHODS: This analysis included 271 children >or=6 years (older group) and 296 children <6 years (younger group) from a family-based FA cohort in Chicago, IL. Asthma was determined by parental report of physician diagnosis. FA status was determined based on the type and timing of clinical symptoms after ingestion of a specific food, and results of prick skin test (Multi-Test II) and allergen-specific IgE (Phadia ImmunoCAP). Analyses were carried out using logistic regression accounting for important covariates and auto-correlations among siblings. Kaplan-Meier curves were used to compare the time to onset of asthma with the FA status. RESULTS: Symptomatic FA was associated with asthma in both older [odds ratio (OR)=4.9, 95% confidence interval (CI): 2.5-9.5] and younger children (OR=5.3, 95% CI: 1.7-16.2). The association was stronger among children with multiple or severe food allergies, especially in older children. Children with FA developed asthma earlier and at higher prevalence than children without FA (Cox proportional hazard ratio=3.7, 95% CI: 2.2-6.3 for children >or=6 years, and hazard ratio=3.3, 95% CI: 1.1-10 for children <6 years of age). No associations were seen between asymptomatic food sensitization and asthma. CONCLUSIONS: Independent of markers of atopy such as aeroallergen sensitization and family history of asthma, there was a significant association between FA and asthma. This association was even stronger in subjects with multiple food allergies or severe FA.