In two different studies (Ramirez De Knott et al., 2006; Johansson et al., 2009) there was no correlation between IgE and atopy patch test for Malassezia, whereas Johansson et al. (Johansson et al., 2003) found that atopic patch test was positive in 30% of AD patients without head and neck dermatitis and in 41% of patients with head and neck dermatitis. Here, IGHE is linked to Alzheimer disease.