IL4 and asthma: The above concepts provide a valid explanation in order to understand the relevant roles played by IgE, IL-5 and its receptor, IL-4/IL-13 receptors, and alarmins/alarmin receptors as valuable targets of currently available and potential future add-on biological treatments of type 2 severe asthma (Figure 1) [28,29,30,31,32,33,34].