IL4 and atopic eczema: In primary keratinocytes, atopic dermatitis cytokines (IL-4, IL-13 and IL-31) significantly decreased mRNA expression of the barrier structure protein filaggrin (FLG) without histamine (0.3 ± 0.06-fold, p < 0.001; Figure 2a) and in combination with histamine (0.24 ± 0.04-fold; p < 0.001; Figure 2a).