CD4 and food allergy: In addition to genetic factors, a number of environmental, cultural, and behavioral factors affect the frequency, severity, and type of allergic manifestations in patients.18, 19, 20, 21 A recent study identified epigenetic differences in CD4+ T cells from children with IgE-mediated food allergies, compared with children without food allergies—differences such as these might contribute to the development of a food allergy.22