IL22 and allergic asthma: On the other hand, it has also been found that IL-22 is essential for the onset of asthma during the sensitization phase as shown by the impaired eosinophil infiltration, decreased levels of inflammatory cytokines and chemokines, and mitigatory allergic airway inflammation in mice deficient in IL-22, but conversely possess protective functions during the effector phase as mentioned above, suggesting a dual role for IL-22 in allergic asthma [49].