The hygiene hypothesis for allergic diseases associated with high IgE levels [13] may also explain the high IgE levels in patients with KD; better hygiene in infancy and young childhood may lead to defects or dysregulation in B cell development, resulting in low amounts of IgG and high amounts of IgE produced by immature B cells, thereby increasing susceptibility to KD. The gene discussed is IGHE; the disease is allergic disease.