Illumina's BeadChips were used to produce expression profiles of nonlesional epithelium from extrinsic AD patients, nonatopic individuals, and psoriasis patients. The use of tissue staining and quantitative PCR to confirm dysregulated intercellular proteins was used. In Using chambers, epithelial bioelectric characteristics were determined. Using a knockdown technique in primary human keratinocytes, the functional importance of claudin-1 was examined. In two separate groups with Atopic dermatitis, 27 haplotype-tagging SNPs in CLDN1 were examined. The gene discussed is CLDN1; the disease is psoriasis.