In contrast, allergens ASWE and HDME both enhanced NK1R expression on CD14+ blood leukocytes regardless of whether subjects had AD or HC, and PPE elicited up-regulation of expression of NK1R on CD14+ leukocytes of HC subjects, suggesting that allergens are likely to contribute to the development of AD via up-regulating NK1R expression on blood CD14+ leukocytes. This evidence concerns the gene TACR1 and Alzheimer disease.