Food allergies are the third most common type of allergy manifest in dogs. Unfortunately, food allergies in dogs are not breed-specific, and thus there are no "safe breeds." They can develop anywhere between 5 months to 12 years of age, though most often they appear between the ages of 2 and 6. An important thing to understand about a potential food allergy is that it develops over time, and a dog can slowly develop an allergic reaction to a food it has safely eaten for months or years beforehand.

It is also important to understand the difference between allergies and intolerances. A food intolerance, for example, might result in diarrhea or vomiting in a dog, much the same way a human might react poorly to spicy or foreign foods. An allergy may not result in overt symptoms such as these, but might be more subtle such as itchy or sensitive skin. Other common symptoms include hot spots, excessive scratching, hair loss, and ear sensitivity/infections. Year-round symptoms are a good tip-off, because seasonal allergies will naturally only appear at certain times. Also, a number of studies have shown that an increase in a dog's bowel movements to three times a day or more could be an indicator of a food allergy, as a healthy dog should typically only move its bowels about 1.5 times a day. Blood tests can also be performed by a vet to help identify potential allergies, though there are some that doubt the validity of the results.

Allergic reactions to food are unfortunately often difficult to diagnose. Because many owners feed their dogs dry or canned dog food with many different ingredients, often the best way to reliably test for food allergies is to put the dog on a strict diet of a new source of protein and a new source of carbohydrates for 12 weeks., such as venison and rice, for example. Assuming the dog's symptoms clear up, the original food or ingredients can be introduced one at a time to the dog's diet to see if the symptoms return. If an offending ingredient is identified, treatment is rather straightforward: simply refrain from feeding it to the pup. It's important to afterwards check the ingredients of any store-bought dog food, since many contain a wide variety of ingredients. Many veterinarians will be able to recommend a special food, and some will sell owners the food directly, though be aware that the specially prepared foods are typically more expensive than common store-bought dog foods.

For particularly sensitive allergies, or for allergies for common ingredients, home-cooked food is always an option. Remember to always consult your vet before putting your pet on a new diet, as the meals need to be properly balanced so that your pet gets healthy amounts of the nutrients he or she needs. However, preparing the dog's meals yourself could alleviate the cost of custom diets.

Although diagnosis can be a long and arduous process, the result is a happier and healthier pet, and a worry-free owner.