Interestingly, the Th2 cytokine IL‐4, in the presence of antigen, is able to promote the development of thymus‐derived Tregs.54 Thus, increased penetration of antigens through the skin, owing to FLG null mutations, might synergize with the immune environment to trigger the expansion of thymus‐derived Tregs in AD patients. Here, FLG is linked to Alzheimer disease.