Focusing on allergic asthma, a susceptible individual’s exposure to aeroallergens leads to activation of the epithelium in the airways and subsequent secretion of the epithelial-derived cytokines known as ”alarm signs” or ”alarmins”: interleukin 25 (IL-25), interleukin 33 (IL-33) and thymic stromal lymphopoietin (TSLP) [46]. Here, IL33 is linked to allergic asthma.