Molecular analysis of the effects of HDM, with or without Aptamin C, on gene expression by HaCaT and primary keratinocytes identified 31 genes, the expression of which was increased significantly by treatment with HDM extract, but decreased significantly by treatment with Aptamin C. One of these genes encodes GDNF, originally identified as enhancing the survival of neurons through increased dopamine uptake [58,59], but was recently reported to be closely associated with inflammation, especially with severe itching in AD [38,58]. Here, GDNF is linked to Alzheimer disease.