In mice, it could be shown that the expression of TSLP (Liu, 2006), IL4, IL5 and IL13 induces atopic dermatitis as well as asthma (Lee and Flavell, 2004), and IL5 knockout mice exposed to allergens are less prone than wild-type to develop skin eosinophilia and epidermal thickening (Spergel et al., 1999). Here, IL4 is linked to atopic eczema.