The study below comprises prospective analysis of patterns of allergen‐specific T‐cell reactivity in a cohort of 23 children bled at'regular intervals from 6–10 weeks to 2 years of age, together with cross sectional studies on panels of cord and adult blood samples. The results indicate reciprocal patterns of responses to dietary and inhalant allergens, the former being frequent in infancy but rare in adults, whereas the latter are preserved and expand between infancy and adulthood. These findings are consistent with a recently proposed model for the development of immunity to environmental allergens which involves allergen‐driven T‐cell “selection” during early life leading to deletion of food allergen‐specific T‐cells via the induction of specific anergy, with concomitant selection and ultimately expansion of mutually exclusive TH‐1‐like or TH‐2‐like reactivity to inhalant allergens via Immune Deviation mechanisms.