Lesional skin of patients with psoriasis or atopic dermatitis is heavily infiltrated with activated T cells that produce proinflammatory cytokines including those designated as Th1 cytokines (e.g. interferon-gamma (interferon-γ) and tumor necrosis factor alpha (TNF-α)) or Th2 cytokines (e.g. interleukin (IL)-4, IL-5 and IL-13). This evidence concerns the gene IL13 and atopic eczema.