In allergy, Th2 cytokines such as IL-4 and IL-13 drive the differentiation of macrophages towards a phenotype referred to as M2 (alternative) activation, which is associated with enhanced expression of characteristic markers, notably including arginase-1, the inflammation-associated protein FIZZ1 (also known as resistin-like α), the chemokine eotaxin-2 (CCL24), and the chitinase-like protein Ym1 [18–20]. Here, CCL24 is linked to allergic disease.