It has been shown that mildly acidic filaggrin breakdown products, that is urocanic acid (UCA) and pyrrolidone carboxylic acid (PCA) execute control over the bacteria in the skin (Miajlovic et al., 2010); reduced level of UCA and PCA in AD contribute to the elevated skin pH and loss of this antimicrobial control mechanism (Kezic et al., 2011). This evidence concerns the gene FLG and Alzheimer disease.