In patients with peanut allergy, in vitro evaluation of the phenotype of peanut-specific CD4+ Th cells by using cutaneous lymphocyte antigen (CLA) as a marker for the epicutaneous rout of initial sensitization demonstrated that higher proportion of CD4+ Th cells expressed this skin-homing molecule (CLA+), indicating activation following exposure through the skin. The gene discussed is CD4; the disease is peanut allergic reaction.