Food Allergies in Pets

2016-10-04 | Food & Nutrition

When your dog or cat has itchy, irritated skin they will typically spend a lot of time scratching, licking, and biting themselves in an attempt to ease their discomfort. This constant scratching can drive many pet owners crazy, so imagine how your pet must feel! There are a number of reasons why your cat or dog might be experiencing itchy skin, including:


Environmental dermatitis: Aspects of your pet’s environment, such as grass, thistles, rain, pond, or lake water, and plants may cause adverse reactions or may lead to lesions that can become inflamed and infected.


Parasitic dermatitis: Fleas and ticks are what many pet owners think of first when their cat or dog begins to scratch themselves excessively. Fleas are dark coloured and around the size of a pin head so easy to spot; they’re also easy to treat with over-the-counter remedies.


Infectious dermatitis: Bacterial, fungal, and yeast pathogens are often responsible for causing skin and coat itching in pets. Environmental factors, such as lesions caused by plants, can open up the skin and allow bacteria to invade and attack.


Allergic dermatitis: There are any number of things that your pet could be allergic to, including dust mites, mould spores, pollen, plants, carpet, blankets, and many other things that you might not expect. Your vet can help you identify the cause.


Neurogenic dermatitis: This is a condition in which your dog will inexplicably lick or scratch an area of skin, causing it to become infected. The wound often heals partially only to be re-infected by over-zealous licking and scratching.


Nutritional dermatitis: As with humans, improper nourishment in pets can lead to skin problems such as itching, flaking, acne, and lesions. Dogs and cats need meat-rich foods, but even then they may experience allergies and intolerances.



Food allergy or food intolerance?

The two terms are often used interchangeably, but there is actually a difference between the two. Food allergies typically exhibit symptoms like itching and skin problems in cats and dogs. Food intolerances, on the other hand, will not normally result in skin problems. Instead, food intolerances will produce symptoms such as vomiting and diarrhoea, in the same way that a human with intolerance to gluten or lactose would experience gastrointestinal distress of some kind.


Many people assume that a food allergy is the response to a recent diet change. However, food allergies actually develop over a prolonged period of time, and in most cases the animal will have been eating the offending food for years without a problem.



What symptoms should you look out for?

The symptoms of a food allergy in dogs are similar to airborne allergy (atopy) and an infectious disease known as sarcoptic mange (canine scabies). The treatment methods for atopy, mange, and food allergies are markedly different from one another, so it’s important that your pet is properly diagnosed by a veterinarian. However, it can sometimes be difficult to determine whether it is scabies or an allergy; if you notice any of the following then it is likely to be a food allergy causing your pet’s itching:


The primary symptoms to look out for are itchy skin affecting the face, feet, ears, forelegs, armpits and the area around the anus.

Also look out for chronic or recurrent ear infections, excessive scratching, hair loss, hot spots, and skin infections that respond initially to antibiotics but reoccur after antibiotics are stops.

Your pet has previously received treatment for sarcoptic mange without any sort of positive change.

Your pet’s itchy skin is not, and has never been, solely a seasonal problem.

Your pet has not responded positively to cortisone-based medications.

A skin biopsy has demonstrated the changes often associated with food allergies.

Your pet is displaying a lesion pattern common for food allergies.

Your pet did not experience skin issues before the age of five or six.



If any of the above applies to your pet, it is a good indication that you should pursue the diagnosis and treatment of a food allergy. Observe your pet over the course of a week or so, and present your findings to the vet in order for them to make the correct diagnosis.


The flea factor: Many animals will experience more than one allergy at a time. For example, it is not unusual for an animal with a food allergy to also be allergic to flea bites. Flea bite allergy is extremely common among pets, and allergies add to each other to produce shared symptoms. A dog with a food allergy may not experience itchy, inflamed skin if their flea problem is under control. Flea treatment is safe and convenient, so it’s easy to eliminate fleas from your pet’s coat and prevent itching.



What causes a food allergy?

A domesticated animal’s diet is typically made up of meat, processed food proteins, fillers, and colourings, all of which are further processed inside the animal’s body. Some of the most common foods associated with food allergies include:

Dairy products
Chicken eggs

Many of these common offenders are ingredients that are usually featured heavily in dog foods, and this is no coincidence. Some proteins may be more antigenic than others, but many proteins have a similar form and the incidence of food allergies could be linked to the amount of exposure to the protein.


The proteins in foods can be combined or changed into other substances which are recognized by the immune system as foreign invaders that need to be attacked. The inflammation that results from this immune response may then target the gastrointestinal tract or other organ systems; however, in cats and dogs, it is the skin that suffers most often from this immunologic activity.



How is a food allergy diagnosed and treated?

As mentioned above, the symptoms of a food allergy (itchy skin and excessive scratching) are the same as a number of other conditions, including atopy, flea bite allergies, sarcoptic mange, bacterial and yeast infections, and parasitic hypersensitivities. All of these potential other causes of skin irritation need to be ruled out before food trials are performed to test for a food allergy.



Food trials and elimination diets

A typical food trial will involve feeding the animal a novel source of protein and carbohydrate, i.e. a food source that they have never eaten before, for at least 12 weeks. For example, you could feed them food that combines venison and potato, or rabbit and rice provided they haven’t eaten it before. Whether you choose to make your pet’s food yourself from scratch, or use one of the specialised brands on offer, it should be the only thing that your pet eats for the full 12 weeks, aside from drinking water.



Tips for a successful food trial:

Feed your pet the same protein and carbohydrate combination for every meal for the full 12 week period.


Do not give your pet any treats, including rawhides, flavoured plastic toys, flavoured toothpastes, flavoured medications, or any other type of food with their medication.


If you are using specialised canned food you can freeze it in chunks to use as small treats.


If you have other pets that feed in the same area you should either feed them the same diet, or feed them in a different room and don’t allow the patient access to that room.


Keep your pet out of the room at family meal times; even a small amount of food dropped on the floor or licked from a plate can void the elimination trial, causing you to start the process again from scratch.


Don’t allow your pet to roam freely; keep cats indoors, and keep dogs on leads when outside in order to avoid them rummaging through garbage and eating foods that they shouldn’t.


Keep a record of the date and time of any foods and treats that your pet may have eaten accidentally.



If the animal shows a marked reduction in symptoms after the 12 week food trial, the original food can be reintroduced. If your pet’s symptoms return within two weeks after going back onto their original diet, the diagnosis of a food allergy can be confirmed. If there is no change in symptoms but a food allergy is still suspected, another food trial can be conducted using a different novel food source.



Ongoing treatment of a food allergy

The main treatment for food allergies is avoidance of the allergen. Once the food allergen has been identified as a result of the food trial, it needs to be eliminated from your pet’s diet completely to avoid a recurrence of symptoms. There are two choices for pet owners: feed the animal a homemade diet, or use special commercially prepared food suitable for the animal’s dietary needs.


If you choose to feed the animal a homemade diet, you can periodically introduce different foods into the mix to test the response. For example if you used lamb and potatoes during the food trial you know those foods are safe, so you can then introduce beef, for example, over a two week period. If beef doesn’t produce any symptoms you could then introduce chicken over the next fortnight; and so on and so on until you have built up a broad and varied menu which is safe for your pet to consume. If the animal shows symptoms during one of the two week periods, it can safely be assumed that the newest food is causing the allergic reaction, and this can thus be eliminated from their diet also.