Adverse food reactions are categorised as reactions to dietary ingredients by specific individuals which are harmless to others. This term covers toxic reactions, food allergies and food intolerances. A food allergy is an immune system response to one or more proteins that have been ingested by the pet, with food intolerance being typically cell-mediated responses, rather than immune-mediated responses. Jennifer Dean of Pets Choice looks at pet food intolerance symptoms, diagnosis and treatment, concluding that identifying ingredients in pet food will help prevent pet discomfort through alleviating allergy symptoms.