There is a difference between food allergies and food intolerance. Food allergies cause skin irritations. food intolerances cause diarrhea or vomiting, but don't cause the usual allergic signs of skin irritations and itching.

Time

There isn't a set time for food allergies to develop. A dog could show signs of a food allergy quickly,  within days. Or it might not show up until eating a dog food for years. When a dog becomes sensitized to a dog food, it is a complicated process that involves an antibody response occurring in his intestinal tract.

Percentage

Dog food allergies occur 70% of the time with a food a dog has eaten for awhile, normally around 2 years or longer. They don't usually occur when the dog  initially eats a certain food. Food allergies are the reason for 20% of the itching that dogs suffer.

Response

The allergic response normally includes skin irritations like rashes, hot spots, and scaly red spots. The dog will shake his head a lot and paw his ears and face. Allergies can also cause other symptoms such as hyper-activity, aggression, chronic ear infections, breathing problems, infections of the eyes or inflammation.

If a dog has the allergic symptoms all the time and not just seasonally that is a clue it it a food allergy. Another clue is if antihistamine isn't effective. One more telltale sign is if a young dog has skin or ear ailments that are chronic.

Common Offenders

Studies have found these foods to be the usual ones to cause food allergies.

- Corn
- Wheat
- Soy
- Chicken
- Beef
- Lamb
- Dairy products
- Fish
- Chicken eggs
- Yeast
- Food coloring
- Preservatives

These foods are commonly used in commercial dog food recipes. Exposure is the key to the incidence of allergic reaction.

Veterinarian

A veterinarian can take blood tests and use other procedures to track down the foods that trigger an allergic reaction in your dog. If the vet thinks your dog has a food allergy, he will recommend an elimination diet, which means removing foods from his diet and giving him a different food regiment. Then after 12 weeks, returning the original foods one by one to look for an allergic reaction.

The foods the vet suggests should be all your dog eats during this elimination time. Do not give him things like treats, raw hide chews or flavored toys, meds or toothpaste. Do not let him near a litter box, outside off of a leash or near another pet's food.

Offending Food

When the offending food or foods are identified the only way to avoid an allergic reaction in the long run is to stop feeding those foods to your dog.  For more immediate relief antihistamines, fatty acids, and steroids are used.

Allergic Prone

Certain breeds of dogs have an allergic response to foods more often than other breeds: boxers, terriers, bulldogs, Irish setters, schnauzers, cocker spaniels, retrievers, and dalmatians. Other kinds of dogs can develop food allergies, but the breeds mentioned are more likely to develop them.