IL17A and Alzheimer disease: Interestingly, though both lesional and non-lesional AD demonstrate epidermal barrier defects as demonstrated by higher TEWL, significantly elevated allergen-specific serum IgE may (extrinsic AD; most frequent) or may not (intrinsic AD; also called non-atopic eczema) be present in symptomatic patients, indicative of two distinct subtypes, with higher IL-17 levels in intrinsic AD (23–25).