While the allergen-induced Th2-lymphocyte, IL-5 mediated, eosinophilic response in asthma is now well characterized [1], recent research has shown that up to 50% of all asthma cases show no evidence of eosinophilic inflammation, termed non-eosinophilic asthma, and a subgroup of these have a persistence of airway neutrophilia, termed neutrophilic asthma [2,3]. This evidence concerns the gene IL5 and asthma.