Does your pet have itchy skin or experience chronic vomiting, diarrhea or paw licking? If so, your pet may be having an adverse reaction to his food.

Both food allergies and food intolerances can cause adverse reactions. Food allergies occur when the immune system reacts inappropriately to a food. Food intolerances are more common and occur without immune system involvement.

The digestive system is an amazing series of organs that not only digests and absorbs food, but also plays a key role in immune function by defending against foreign invaders that cause illness. The immune system must act quickly and aggressively to protect against potentially harmful substances, but also know when to remain unresponsive to food.

In the case of a food allergy, the immune system mistakenly identifies a food as harmful, instead of nourishing, and it kicks into overdrive. This results in undesirable symptoms, and severe allergies can even be fatal. The symptoms of food intolerance are often quite similar to food allergies, though they are usually less severe and are not life-threatening.

Food reactions in pets often mimic other conditions, such as environmental allergies to pollen and grass, and diagnosis can be challenging. Blood and skin-patch testing are available for a variety of potential food allergens, but do not always provide a clear answer because many food ingredients can show a false positive or incorrect result.

However, these tests may still provide valuable information about potential problem foods to investigate further. If an ingredient does not show a reaction on skin or blood reaction tests, it is a suitable choice for inclusion in an elimination-challenge test, as described below.

Most food allergens are proteins, so this is the component to consider when trying to determine the offending ingredient. The number of different proteins, the protein sources and whether the pet has been previously exposed to the protein are the major factors to consider when selecting a diet for a food-intolerant pet.

The length of time a pet has been on a food does not seem to affect the risk of developing adverse food reactions. A pet can react to a food after just one feeding, or after many months or years on the same food. Just like people, every pet is different, so the degree of sensitivity to an ingredient will be variable. For some pets, trace quantities of the ingredient may cause a problem, whereas others might have a higher tolerance level.

With adverse food reactions seemingly on the rise among dogs and cats, many pet parents are looking for solutions. Limited-ingredient diets with novel protein and carbohydrate sources, hydrolyzed protein diets and home-cooked elimination diets have all been reported to be useful.

Limited-ingredient diets

A limited ingredient diet (LID) offers a single source of meat protein with as few additional ingredients as possible to meet the nutritional requirements of your pet. A novel ingredient is an animal or plant that is not commonly used in pet foods or is not commonly associated with adverse food reactions.

Novel protein and carbohydrate ingredients are typically used in LID recipes to increase the chances of success. Some of the novel meat sources used may be venison, bison, kangaroo or rabbit. For carbohydrates, ingredient options include tapioca and pulses such as peas, lentils and garbanzo beans (chickpeas). Since fats and oils do not contain protein, the fat source in the diet is not usually considered a concern.

In order to determine whether an LID recipe will work for your food-sensitive pet, it is important to remember that this diet is the only food your pet should eat. You should eliminate most treats and other food sources. There may be treats available that contain only the specific ingredients used in the LID recipes, but ingredients other than these should be avoided.

Once you start the LID recipe, you may notice an immediate improvement in the health of your pet. However, your pet should stay on the new food for at least 8-12 weeks to ensure it is the right choice.

Hydrolyzed protein diets

A diet containing hydrolyzed proteins is another option for food-intolerant pets. These are specialized diets that are typically available through veterinarians. The protein has undergone a process to hydrolyze, or break down, the protein into smaller fragments so they are less likely to cause a reaction.

Because the protein itself is modified, the actual source of the protein (chicken, beef, turkey, etc.) is likely not as important. The smaller the protein fraction size, the better when it comes to solving food sensitivities.

Home-cooked elimination diets

Home-cooked diets are another possible solution for pets experiencing adverse food reactions and can be helpful to pinpoint the offending ingredients. The "gold standard" to diagnose an adverse food reaction is a food elimination-challenge trial.

An elimination diet is a specialized diet that is fed to the pet and excludes all suspect ingredients. These are often home-cooked diets, in order to carefully control the ingredients included. Once a diet is found that resolves the symptoms, the pet is then fed the aggravating ingredient to see if symptoms reappear. If they do, then an adverse food reaction is confirmed.

Elimination-challenge trials can be difficult for pet parents to follow because they are so strict. They need to be closely monitored by a veterinary medical or nutrition professional since elimination diets are often nutritionally incomplete or unbalanced, and they should not be fed over the long term.

The elimination diet will need to be followed for approximately 6-8 weeks to completely determine success. Elimination-challenge trials are a lengthy process, particularly if the pet reacts to multiple ingredients, but they are necessary for a definitive diagnosis and worth it in the long run for the pet's well-being.

It may take some trial and error to find a food that works for a food-sensitive pet, but in the long run your pet will thank you for your patience and persistence.