FLG and Alzheimer disease: A reduction in filaggrin breakdown products on AD skin, either because of FLG null alleles or secondary to a TH2 inflammation–driven decrease in FLG expression, may increase expression of staphylococcal IsdA and could promote increased survival of S aureus. Fatty acids found on skin such as oleic acid and antimicrobial peptides such as dermicidin I are more effective at killing S aureus at pH 5 than at neutral pH.