Allergic diseases are common in dogs and the involvement of IgE in the pathogenesis of canine atopic dermatitis (CAD) and flea allergy dermatitis (FAD) is documented. However, many dogs do not achieve sufficient control of their allergic disease, and there is a great need for new treatment strategies. In order to address this issue we first needed to obtain a better picture of IgE-levels in dogs and how plasma IgE-levels are affected by breed, age and health status. IgE is normally present at diminutive concentrations in sera and detection by diagnostic methods has been a technical challenge. Here, we present a new in vitro assay for determining absolute levels of total IgE in sera from dogs. In a panel of 76 adult dogs diagnosed either as healthy or suffering from atopic dermatitis, autoimmunity or infection by skin parasites, we show that levels of IgE range from 1 to 41 microg/ml. This is almost 100 times the level observed in non-atopic humans. However, these exceptionally high IgE-levels in the dogs could not be correlated to either breed or health status. To address the issue of novel treatment strategies, the possibility of reducing the IgE-levels in nine Beagle dogs by immunization with a new therapeutic vaccine was investigated. High levels of anti-IgE antibodies were induced in all dogs, and the IgE-levels were subsequently decreased by a mean of 65%. This shows that the allergy vaccine is potent enough to break the tolerance against IgE, even when the initial IgE-levels are as high as those observed in dogs. Thus, the vaccination treatment may have the potential to serve as a future therapy for dogs with atopic diseases.