CCL17, produced by Th2 cells and keratinocytes, is a key chemokine involved in homing of CCR4‐expressing T cells to the skin.45 CCL17 has been detected in the inflamed skin of patients and in an animal model of AD.46, 47 Serum CCL17 is strongly correlated with disease severity in patients with AD, including infants, and is the most reliable objective AD biomarker identified to date.48, 49, 50, 51 CCL22 is similar to CCL17 and is a chemoattractant for CCR4‐expressing skin‐homing T cells.46 Here, CCR4 is linked to Alzheimer disease.