Around 10% of all allergies in dogs are caused by a reaction to food groups, and they can occur at any time in a dog's life. Unfortunately, allergies aren't always easy to identify. When your dog has an allergic reaction, an antibody is produced that can sometimes be spotted in an allergy test, but the results are often unreliable. Don't confuse an allergy with a food intolerance; the latter are foods your dog finds hard to digest and may result in diarrhoea and vomiting. There is no direct test for food intolerances.

Causes
There are some common human foods that a dog's digestive system is just not designed to cope with. These include rhubarb, soya, onions, spinach, beetroot, and undercooked maize or undercooked kidney beans. Other irritants (in order of commonality) include beef, dairy products, chicken, wheat, chicken eggs, corn and soy.

Symptoms
Typical symptoms of food allergies include;

• Itchy skin.
• Recurrent ear infections.
• Scratching.
• Hair loss.
• Skin abrasions
• Vomiting.
• Diarrhoea.

Testing for allergies
The most effective method of testing for an allergy is a 12-week trial, where a food is withdrawn from the diet and then reintroduced to see if it has any effect on the symptoms. As most sources of pet food are made up of beef, chicken, corn and wheat, it helps to switch to a food that your dog hasn't eaten yet, such as lamb and rice, venison and potato or rabbit and rice. This new food must be the only thing the animal eats for the duration of the trial, which should be conducted under veterinary supervision.

After the trial period
Once your dog has finished the 12-week trial period, try introducing one element of the old diet each week, such as chicken, eggs, soy, etc. to see how your dog reacts to each. If the symptoms return when a food is reintroduced, you'll have your culprit!