As basophils and mast cells can produce β-HEX, IL-4 and IL-5 after allergen stimulation, and secreted enzymes such as tryptase can induce the release of β-HEX from eosinophils in the blood [44], these molecules may engage in both the induction and exacerbation of asthma through positive feedback loops. This evidence concerns the gene IL5 and asthma.