When nasal polyps accompanying chronic sinusitis were classified on the basis of being atopic or nonatopic (determined by allergy skin testing) and their cytokine profiles were analyzed, it was found that IFN-γ expression was increased in the nonatopic nasal polyps, whereas IL-4 and IL-5 expressions were increased in the atopic nasal polyps [3]. Here, IL4 is linked to allergic disease.