Complex sentence: Allergic reactions in the lung typically have two phases, in which the late phase typically occur several hours after exposure, in which eosinophils accumulate in the bronchus and resease granule proteins that causes bronchial irritability.
Split into simpler sentences: Allergic reactions in the lung typically have two phases. The late phase typically occurs several hours after exposure, upon which eosinophils accumulate in the bronchus and release granule proteins that cause bronchial irritability.