Specific IgE antibodies and serum eosinophil cationic protein in children with atopic dermatitis alone

Both eosinophils and specific immunoglobulin E (IgE) to foods and mites have been considered involved in the pathogenesis of atopic dermatitis (AD). The relationship between eosinophils and specific IgE, however, remains to be elucidated. Blood eosinophil counts, serum eosinophil cationic protein (ECP) and IgE to egg white, cow's milk, soybean, rice and Dermatophagoides pteronyssinus (Dp) were measured in subjects with AD alone or bronchial asthma (BA) alone. Subjects with positive IgE titers (Pharmacia radioallergosorbent test (RAST) units > 0.7) of one or more items were defined as RAST-positive. Immunoglobulin E titers to egg white, cow's milk and soybean of subjects with AD were high in early childhood and declined with aging, whereas the titers of subjects with BA were negative or low. Immunoglobulin E titers to Dp were elevated after 1 year of age in both disease groups. Eosinophil cationic protein (ECP) levels and blood eosinophil counts in the AD and BA groups were significantly higher than those of non-atopic controls. No difference in ECP levels or blood eosinophil counts were observed between RAST-positive and negative groups. It is concluded that IgE to foods such as egg white, cow's milk and soybean might have a role in the pathogenesis of AD of young children, while IgE to mites might be involved in older children. Eosinophils may also participate in AD. However, different mechanisms may be responsible for the rise in specific IgE and high ECP levels and blood eosinophil counts.