The significance of allergen-specific IgE as marker for severity of atopic dermatitis is controversial. The aim of this study was to determine the frequency of IgE-mediated sensitisation to food and environmental allergens in 132 children and 67 adults with atopic dermatitis, and its correlation to severity of atopic dermatitis (SCORAD). Total IgE was elevated (> 100 kU/l) in 79.7% of adults and 46.8% of children. Sensitisation frequencies to allergens, particularly microbial allergens, were up to 10-fold higher in adults compared to children. Severity of atopic dermatitis correlated with elevated total IgE in adults (r = 0.549, p < 0.001) and children (r = 0.344, p = 0.005) and with Malassezia spp.-specific IgE in adults (r = 0.429, p = 0.007). Total IgE is a marker for severe atopic dermatitis in both age groups. Malassezia spp.-specific IgE is an important allergen-specific marker for severity of atopic dermatitis in adults.