Allergies to food are fairly common in dog. Allergic reactions occur within minutes or a few hours after the food is eaten and signs can include:
- itchy skin (pruritus) on the feet, ears, face etc.
- gastrointestinal problems like vomiting, diarrhea and gas
- coughing, sneezing and wheezing
- in rare cases, anaphylaxis (which is a severe, life-threatening adverse reaction involving the major body systems).
In a review of clinical studies that looked at the foods which cause dog food allergies, beef, dairy products and wheat accounted for 69% of reported cases while lamb, chicken egg, chicken and soy accounted for 25% of the dogs.
Food allergies occur when the dog's immune system reacts to a protein (allergen) from a particular food that has been swallowed. The allergen causes the dog’s own antibodies to attack the foreign substance. In dogs with food allergies, the immune system produces increased amounts of immunoglobulin E antibody, or IgE. When these antibodies battle with food allergens, histamine and other chemicals are released. These chemicals cause blood vessels to widen, smooth muscles to contract and affected skin areas to become red, itchy and swollen.
Food sensitivities / intolerances are different from food allergies, in that sensitivities involve the digestive system, but not the immune system. However, as both food allergies and food intolerances can cause skin itching, both are sometimes grouped together under a single name, "Cutaneous adverse food reaction (CAFR)".