Children without a history of tree nut related symptoms and with low levels of sIgE to all tree nuts were challenged with six nuts (almond, walnut, cashew, pistachio, pecan, Brazil nut) (protocol A), Children with suspected cashew/pistachio allergy (previous symptoms or a specific IgE to cashew or pistachio of > 10 kU/L) were challenged with four nuts (almond, walnut, pecan, Brazil nut) (protocol B). The gene discussed is IGHE; the disease is allergic disease.