Flea allergy dermatitis reactions are common in cats. The researcher believes it is likely that the immune system of a kitten learns to recognize the flea as non-foreign through a mechanism known as tolerance. Immunologic tolerance is a basic property of the immune system that allows an individual to come in contact with substances without developing adverse reactions to them. For over 100 years, it has been known that early ingestion of different foods can serve as a method of oral tolerance to prevent later unwanted immune reactions such as food allergy. This pilot study will evaluate the role of early exposure to fleas in the development of flea allergy and the findings will contribute important information concerning what happens to cats when they develop allergic reactions to fleas. Information gained in this study may lead to development of a vaccination or other strategy to prevent or minimize allergic reactions to fleas in cats.