Why does classic scabies spare the adult scalp? A site-specific barrier hypothesis

Dear Editor, The relative sparing of the scalp and face in immunocompetent adults with classic scabies is clinically familiar, whereas these sites may be involved in infants, older adults, immunocompromised patients, and crusted scabies. This distribution is commonly used as a diagnostic clue, but its biological basis remains incompletely explained. [...].