There is widespread use of serum allergy tests which are promoted for identifying the reaction against certain allergens in atopic dermatitis, sarcoptes infestation and also food hypersensitivity in dogs. Around 20 years ago the first in-vitro tests were developed to identify allergen-specific IgE in dogs with atopic dermatitis. Since then, technical developments have markedly improved the quality of antibodies as well as the methods. The limitation of serum tests lies in the interpretation of test results as well as the diseases they are used for. This overview discusses usefulness and limitations in different skin diseases.