Canine food intolerances: what’s in your dog’s food bowl?

For our canine friends, the filling of the food bowl is one of the highlights of the day. But what if the food your dog loves gives him problems? Dogs with food intolerances often suffer from digestive or skin problems. But pinpointing the problem ingredient will help your dog live a full and healthy life. Read here what you can do and which herbs are useful in treating food intolerances.

What is food intolerance?

The collective term food intolerance (or food sensitivity) in dogs refers to several different diseases that manifest themselves through digestive disorders or skin problems, and are caused by the ingestion of certain foods. Whilst healthy dogs have no problem with these foods, dogs with food intolerances experience a variety of reactions. A food allergy, for example, is an exaggerated reaction of the immune system to certain food allergens. A food intolerance, on the other hand, might be caused by a deficiency of certain digestive enzymes. Other causes include bacteria or mould in the food. Abnormal reactions to food components such as histamines may also occur. The result is an allergic reaction. It is hard to distinguish food allergies from food intolerances, as the symptoms are similar in both.

How do food intolerances occur?

Scientific studies show that canine food intolerances first develop when the animal is quite young. In its first weeks of life, a pup must develop an active, individual immune response to food; this is known as “oral tolerance”. The gastrointestinal tract learns to recognise and tolerate the ingested nourishment as easy to metabolise in preparation for exposure to a variety of food allergens after the pup is weaned. If there is a disruption in the complex interplay between immune cells and bowel tissue, for example from being overwhelmed by too many different nutrients, this increases the risk of later intolerance reactions. When you bring a puppy home, introduce it to food changes slowly so that the organism can adjust to the new ingredients. Diseases that cause increased permeability of the intestinal mucosa, for instance viral diseases with diarrhoea, can also lead to the development of food intolerances. And finally, immunodeficiencies like selective immunoglobulin A (IgA) deficiency can lead to a dog’s increased sensitivity to certain foods. Although dogs can develop food intolerances at any age, the first symptoms are often noticed in the first year of life. Certain breeds appear especially susceptible, including Boxers, German Shepherds, Cocker Spaniels, Springer Spaniels, Dalmatians, Retrievers, Dachshunds, Setters, Shar Peis, and West Highland White Terriers. Afflicted dogs often display additional allergic reactions to flea saliva and environmental allergens, which can make diagnoses difficult.

Which foods are known to cause food allergies?

Basically, all proteins in dog food are initially foreign to the dog's organism and can be potential allergens, but only a small number of proteins trigger allergies. An allergic reaction depends on the permeability of the bowel for this protein and on the immune system’s ability to tolerate the protein. Topping the list of allergens are beef, milk products, and wheat. Studies have shown that over 65% of all allergic reactions can be attributed to these protein sources. About 25% of intolerances are caused by chicken, eggs, lamb, fish, or soya. An unpublished study by the University of Veterinary Medicine in Vienna found that dogs had reactions to cheese, cereals, pork, beef, horse meat, milk, lamb, chicken, rice, bread, fish, turkey, and potatoes.

The allergy potential of proteins can be both increased and reduced by how the food is prepared. This is why many dogs with food sensitivities tolerate canned food less well than fresh food. A special treatment called hydrolysis breaks down the proteins in the food so that they are no longer recognised by the organism as complete allergens. Hydrolysed dog food is often recommended for dogs with food sensitivities, but is often enhanced with flavourings because many dogs do not like the taste. Some dogs have reactions to hydrolysed allergens, so there’s no 100% guarantee of success.

What are the symptoms in a dog with a food intolerance?

• Digestive complaints: In affected dogs, the symptoms are similar to those of chronic inflammatory gastrointestinal disease. Common symptoms include vomiting, abdominal pain, frequent defecation and/or diarrhoea. Long term, these symptoms lead to loss of appetite, stunted growth, or weight loss.
• Skin problems: The most common symptom is itching, either over the entire body or in specific areas such as the ears, face, paws, armpits, or the anal area. Itching caused by food intolerances occurs independent of the season and can fluctuate in intensity. Constant scratching can lead to skin infections that can severely affect the dog. Other dogs experience dandruff, chronic ear infections (Otitis externa), or painful inflammations between the toes (Pododermatitis).
• Cold-like symptoms: Coughing, sneezing, and reddened eyes can also point to a food intolerance.
• General condition disorders: Fatigue, irritability, loss of appetite and listlessness are often associated with food sensitivities.

But a dog with a food intolerance need not have all the symptoms listed above. Some dogs are more prone to skin problems, others experience frequent defecation – more than three times a day – with varying faeces consistency. Symptoms may be solely skin-related or gastrointestinal.

How are food intolerances diagnosed?

When diagnosing a food intolerance, other causes for the dog's symptoms are first investigated. Young dogs especially, or dogs that are "hoovers", will find and eat all kinds of things that are not really beneficial to their gastrointestinal tracts. Worm infestation or faulty diet must also be ruled out as causes of digestive disorders. In the case of skin problems, underlying diseases can include parasite infestation, deficiencies, autoimmune diseases, leishmaniasis, and above all atopic dermatitis. The gold standard for diagnosing a food intolerance consists of several steps. First, the dog is put on an elimination diet for 8 to 12 weeks. If symptoms lessen considerably, the dog is then re-introduced to its regular food (“provocation”). If the symptoms return and disappear again when the elimination diet is resumed, the diagnosis is clear.

Additional provocation tests can be carried out for individual ingredients to narrow down the intolerance more precisely. Other foods are given to the dog by degrees and discontinued if reactions occur. Only one allergen is tested over a two week period. However, most dog owners are happy when their dog is no longer suffering and do not continue with further tests.

Other allergy tests, such as contact patch tests or blood tests, are considered rather unreliable or inconclusive for the diagnosing food intolerances. Many food intolerances are not allergy-related.

Eliminate incompatible feeds

What’s in an elimination diet?

To truly eliminate problem foods, the dog’s elimination diet must consist of a protein and carbohydrate source that it has never been given before.

The first thing the vet will need is a list of everything the dog is regularly given to eat or habitually eats, such as the remains of cat food. The list should also include any medications or supplements as well as chew bones or table scraps. This is not always easy to do, but it’s necessary. Because such a list is needed when creating the right elimination diet for the dog. Focus a limited number of ingredients. Try new protein sources that are easy to digest. Also look for a lower protein content in comparison to conventional dog food. Avoid additives. Any rewards and treats must consist of the same ingredients in the elimination diet. You will usually need to give your dog extra vitamins and minerals. Young, growing dogs should get a suitable complete feed to prevent deficiencies. If there are other dogs in the household, feed them separately or, to be safe, put them all on the same elimination diet.

This will be a hard time for the dog owner. To confirm a food intolerance, the dog may eat just what’s on the menu and nothing else, whether at home or while out and about. A single "find" while being walked, a tiny morsel of biscuit or bit of sausage that "fell off the table", and all the effort will have been for nothing. This demands an enormous amount of discipline and attention from the owner. Muzzle your dog when going for walks; otherwise, leisurely strolls with friends or looking at your smartphone will be taboo. At home, the whole family has to be involved, even Granny who feels sorry for the “poor dog” and the children who want to sneak a little something to their buddy. Friendly visitors who bring dog treats must be told to replace these with diet-compatible ones.

Well, what can I feed my dog?

Your vet will have hypo-allergenic ready-to-eat dog food made of rarely used protein and carbohydrate sources. These special foods are labelled "suitable for elimination diets" and are made specially for dogs that have reactions to several food ingredients. The problem here is that you must rely on the manufacturer's information and can never be completely sure which ingredients have been used to make it. Terms like "fats”, “dietary fibre”, and “vegetables" do not allow any precise conclusions to be drawn about what may be causing the reactions.

Can I prepare an elimination diet for my dog myself?

Home-prepared elimination diets that consist of only two ingredients often bring results faster than manufactured foods. However, preparing an elimination diet takes time and can be quite expensive for large breeds, as they should be fed only high-quality meat, meaning no offal or leftovers containing hard-to-digest connective tissue like tendons. In addition, the meat must not come in contact with proteins from other types of animals. The ingredients must not even be cut on a cutting board contaminated with foreign substances – for example, the meat you tenderised on it for Sunday dinner.

What protein sources are permitted?

Obtaining a suitable protein source for an elimination diet is often difficult, as often the only meats that remain are venison, rabbit, ostrich, and the like. Another option is horse meat, but many dog owners reject it on ethical grounds. The selection is further complicated by the possibility of allergic cross-reactions between the meat of individual animal species. For example, a dog might have reactions not only to beef, but also to dairy products or to the meat of other ruminants like sheep, goat, deer, or even completely different mammal species such as pig or kangaroo. Feeding raw meat is not advised in elimination diets, as raw meat is often infested with bacteria. The same hygiene standards should be applied during preparation as when cooking for the family.

What carbohydrate sources are permitted?

Recommended sources include rice, potatoes (better still, sweet potatoes), and the "pseudo-cereals" amaranth, quinoa and buckwheat. To help digestion, cook rice and potatoes longer than you would for your own meal. Einkorn, Grünkern, spelt, and emmer are all subspecies of wheat and should therefore not be used in elimination diets. 

What can I add to my dog’s food?

You can add vegetable oil to increase the energy content – however, select a kind that is not used in conventional foods, such as pumpkin seed or safflower oil. Avoid prepared mineral mixes, which often contain yeast.

May my dog eat fruits and vegetables?

Fruits and vegetables should not be part of an elimination diet. Particularly problematic are vegetables that are high in protein, such as soya or beans, which for these purposes can be treated the same way as meat. In the provocation phase you can determine which fruits and vegetables the dog tolerates. A special danger is cross-reactions from pollen and ingested fruits, for example birch pollen and apples.

You’ve found the trigger! Now what?

Once the trigger of the intolerance is identified, you can adapt your dog’s food to his specific needs. Your vet can recommend a special hypo-allergenic food or help you to create a diet plan. It is quite possible that your food-sensitive dog cannot tolerate any conventional dog foods at all. The reasons may include their manufacture, storage, or contamination with foreign allergens (such as colourings or flavourings). Dry dog food may have storage mites. That leaves us with home-cooked meals. It is not uncommon for a dog to eat a certain food for years without problems, but then develop an intolerance practically overnight. It is possible that new intolerances have developed from contact with new allergens. In this case, you will need to make adjustments to his feed or give him different foods altogether.

Will herbs help my food-sensitive dog?

If your dog tolerates herbs well, you can use them to increase his well-being. There are many herbs that help to soothe a dog’s sensitive stomach and maintain the natural function of the stomach lining.

• Marsh-mallow contains mucilaginous substances that soothe irritated gastric mucosa.
• Liquorice root is effective against gastric mucosal irritation and inflammation.
• Camomile soothes sensitive mucous membranes.
• Speedwell is a gentle folk remedy for stomach complaints.
• Yarrow is a herb recognised in traditional medicine for treating mucosal inflammation and dyspeptic complaints.
• Walnut leaves have astringent and anti-inflammatory properties.
• Lavender has relaxing and soothing effects.

Food intolerances can severely challenge a dog's organism. It can make an animal’s liver and kidney work overtime. Supporting your dog’s metabolism will help with the elimination of harmful substances.

• Milk thistle fruits help to take strain off the liver and support liver cell regeneration. 
• Artichoke promotes healthy liver and bile function.
• Goldenrod is a diuretic and detoxifying herb.
• Dandelion and birch leaves have mildly diuretic effects and support the elimination of harmful substances via the kidneys. They also boost metabolism.

Important: If you feed your dog herbs, pay close attention to how he is feeling. Your dog’s body may not tolerate a certain herbal substance and develop new symptoms, in which case you should stop using the herb immediately. Do not feed herbs to a dog on an elimination diet.

Sources

• https://laboklin.com/at/frequently-asked-questions/allergy/food-allergy/ , abgerufen am 22.10.2021
• https://www.vetepedia.de/gesundheitsthemen/hund/ernaehrung/unvertraeglichkeit , abgerufen am 21.10.2021
• Nina Diezmann: Futtermittelallergie und Canine Atopische Dermatitis beim Hund – eine retrospektive Studie. Diplomarbeit Vet.med. Univ. Wien, Dezember 2020 (=https://phaidra.vetmeduni.ac.at/open/o:664), abgerufen am 21.10.2021
• K. Widmann: PCR-Nachweis von nicht deklarierten Antigenen in kommerziellen Eliminationsdiäten für Hunde. Diplomarbeit Vet.med. Univ.Wien, Mai 2014, (= https://www.vetmeduni.ac.at/hochschulschriften/diplomarbeiten/AC12248808.pdf), abgerufen am 22.10.2021