Sasikala* , G. Vijayakumar, E. Venkatesakumar, S. Sivaraman, R. Ravi, and P.K. Ramkumar**
As per the recommendations of the American Academy of Allergy, Asthma and Immunology, food allergy (food hypersensitivity) is an adverse reaction to a food or food additive with a proven immunologic basis, which can be IgE mediated and or non IgE mediated immunological reactions. Food intolerance is a non immunologic, abnormal physiologic response to a food or food additive.
Signalment – There is no gender predisposition for food allergy or food intolerance. Similarly, most investigators found no breed predilections for dermatological kind of food allergy. But some have found that Cocker Spaniels, Springer Spaniels, Labrador Retrievers, Collies, Miniature Schnauzers, West Highland White Terriers, Wheaten Terriers, Boxers, Dachshunds, Dalmatians, Lhasa Apsos, German Shepherds, and Golden Retrievers are at increased risk. Similarly, there are no well documented breeds predisposed to gastrointestinal kind of food allergy or food intolerance also. However Chinese Shar-Peis and German Shepherds are more commonly affected with food intolerance. Similarly, gluten sensitive enteropathy has been well documented in Irish Setters.
Symptoms in food allergy are mainly cutaneous, but generally, in about 10-15 % of these cases, gastro intestinal symptoms are also seen. The symptoms in food intolerance are gastrointestinal and do not create a typical allergic response. Food intolerance in pets would be similar to people who get diarrhea or an upset stomach from eating spicy or fried foods. Both food allergy and intolerance can be eliminated with a diet free from offending agent.
- Food allergy can cause a wide variety of lesions and can be considered in any non-seasonal pruritic dog. However, it is also important to recognize that food allergy may be episodic or seasonal, such as when offending food items are given sporadically or when food hypersensitivity symptoms are minimal but aggravated to a clinically significant level with concurrent seasonal atopic disease.
- Pruritus, with or without a primary eruption, is the only consistent finding.
- There is no classic set of cutaneous signs pathognomonic for food hypersensitivity in the dog. A variety of primary and secondary skin lesions are noted. These include papules, plaques, pustules, wheals, angioedema, erythema, ulcers, excoriations, lichenification, pigment changes, alopecia, scales, crusts, and moist erosions, which appear as areas of pyotraumatic dermatitis. Eosinophilicvasculitis presenting as urticaria, or any lesions of vasculitis have been reported.
- Any distribution of skin involvement may occur, but the ears, rump, distal limbs, axillae and groin appear commonly affected. In some dogs, disease is limited to the ears or rump area.
- Pruritic, bilateral otitis externa (frequently with secondary bacterial or Malassezia infections), along with secondary seborrheic skin disease, bacterial pyoderma, or both are common in conjunction with food hypersensitivity. It is observed that chronic otitis is observed in 56 to 80% of food allergic cases.
- Every level of the GI tract can be damaged by food allergies. In dogs, clinical signs usually relate to gastric and small bowel dysfunction though colitis can also occur.
- Vomiting and diarrhea are the prominent features. The diarrhea can be profuse and watery, mucoid, or hemorrhagic. Intermittent abdominal pain is occasionally observed. Concurrent cutaneous signs may be also seen.
- GI disturbances such as soft feces, excessive flatus, intermittent diarrhea, and frequent defecation (three or more times per day) occur in up to half of dogs and cats with cutaneous manifestations of food sensitivity.
- Besides, food allergy may have a role in inflammatory bowel disease and irritable bowel syndrome in dogs.
It is an acute reaction to food with systemic consequences, but most commonly exhibited in localized form i.e. angioedema or facioconjunctival edema. Symptoms noticed include large edematous swelling of the lips, face, eyelids, ears, conjunctivae and / or tongue, with or without pruritus.
Dietary items that have caused food hypersensitivity in a dog:
|Artificial food additives||Horse meat|
|Canned foods||Lamb and mutton|
|Dairy products (whey)||Potatoes|
|Dog foods||Rice flour and rice|
- Routine laboratory blood tests are not useful in diagnosing food allergy or food intolerance.
- At the present time, intradermal skin testing, radioallergosorbent tests (RASTs), and enzyme-linked immunosorbent assays (ELISAs) for food allergy are considered unreliable in animals. The only way to accurately diagnose food allergy is with a food trail.
- Response to dietary trial and provocative exposure testing may be useful.
- Dietary elimination trials are the main diagnostic method used in dogs and cats with suspected food allergy or food intolerance.
- The ideal elimination diet used in the diagnosis and management of food allergy should contain an ingredient that is either novel to the animal or in a form that does not incite an adverse response.
- But as many other problems can cause similar symptoms and that many times animals are suffering from more problems than just food allergies, it is very important that all other problems are properly identified and treated prior to undergoing diagnosis for food allergies. Atopy, flea bite allergies, intestinal parasite hypersensitivities, sarcoptic mange, and yeast or bacterial infections can all cause similar symptoms as food allergies. So after all other causes have been ruled out or treated, then only one should perform a food trial.
- In case of dogs with gastro intestinal symptoms, thorough clinical examination using the Canine Chronic Enteropathy Disease Activity (CCEDA). Faecal examination and other laboratory testing (blood samples and urinalysis) helping to rule out other causes of gastrointestinal symptoms are recommended.
- A complete diagnosis can only be made on the basis of a systematic approach to each patient and careful testing with a home-prepared novel protein diet or a commercially available hydrolysed protein diet. If a response is not observed at once, then another hydrolysed protein diet should be tried.
The Ideal Elimination Food Should…
- Include a protein hydrolysate or reduced number of novel, highly digestible protein sources, avoiding protein excesses, additives, and vasoactive amines and benutritionally adequate for the animal’s life stage and condition.
Novel Protein Diets
- Most novel protein diets have one carbohydrate and one protein source. After a detailed history of the patient’s diet is reviewed, a trail diet with a novel protein is selected on the assumption that the protein has not been fed before.
- For example, if we are treating the patient for chicken intolerance, then intolerance to other poultry meats is considered possible and turkey or duck based diets also are avoided.
Homemade Elimination Foods
- Home cooked diets are advocated to avoid pet food additives that may cause adverse reactions. These foods are often recommended as the initial test food for dogs and cats with suspected food allergy.
- Homemade test foods usually include a single protein source or a combination of a single protein source and a single carbohydrate source.
- In general, homemade foods lack a source of calcium, essential fatty acids, certain vitamins and other micronutrients and contain excessive levels of protein, which are contraindicated in animals with food allergy. Feeding nutritionally inadequate homemade foods for more than 3 weeks may result in nutritional disease, especially in young animals.
Commercial Elimination Foods
- The newest concept for managing animals with suspected adverse food reactions is the use of commercial foods containing hydrolyzed protein ingredients. Veterinary therapeutic foods containing protein hydrolysates offer several hypothetical advantages over traditional commercial or homemade elimination foods.
- Protein hydrolysates of appropriate molecular weight (less than 10,000 daltons) do not elicit an immunologically mediated response and may be regarded as truly ‘hypoallergenic’ ingredients.
Performing an Elimination Trial in Patients with Dermatologic Disease
- Before an elimination trial is initiated, the client should feed the animal its usual food for several days. During this time, the client should record the type and amount of food ingested, any other ingested food items (e.g. table scraps, treats, and snacks) and the occurrence and character of adverse reactions.
- The patient is then fed a controlled elimination food for 4 to 12 weeks. During the elimination trial, no other substances should be ingested, including treats, flavoured vitamin supplements, chewable medications, fatty acid supplements, or chew toys.
- The client should document daily the type and amount of food ingested and the occurrence and character of adverse reactions.
- A tentative diagnosis of an adverse food reaction in dermatologic patients is made if the level of pruritus markedly decreases. This improvement may be gradual and may take 4 to 12 weeks to become evident.
- A diagnosis of an adverse food reaction is confirmed if clinical signs reappear 10 to 14 days after the animal’s former food and other ingested substances are offered as a challenge.
- Elimination trials are often difficult to interpret because of concurrent allergic skin disease. Patients with other allergic diseases may only partially respond to an elimination trial.
- Flea-allergy and atopic dermatitis are the most common canine and feline allergies and should be eliminated through other diagnostic testing.
Performing an Elimination Trial in Patients with Gastrointestinal Disease
- Elimination-challenge trial designs for patients with GI food disease are similar to those for patients with dermatologic problems. However, shorter elimination periods (2 to 4 weeks) are usually satisfactory.
- In chronic relapsing conditions, the elimination period chosen must be greater than the usual symptom-free period of the patient to allow reliable assessment of how food sensitivity contributes to the patient’s signs.
- As with skin disease, the degree of clinical improvement during the elimination trial will be 100% only if food allergy or food intolerance is the sole cause of patient’s problems. For instance, resolution of allergies acquired as a result of GI disease will not eliminate the clinical signs due to the primary GI disease process.
- Recrudescence of GI signs after challenge of a food-sensitive patient with the responsible allergen usually occurs within the first 3 days but may take as long as 7 days, particularly, if the responsible allergen was removed from the food for longer than 1 month.
- For most food allergies, avoiding the offending foods is the most effective treatment. For achieving this, the owner can go for homemade food or a special commercial food.
- It is very important that any homemade recipe for long-term maintenance ensures a nutritionally adequate ration. When homemade diets are given, grinding or blending the protein source in a food processor can be helpful in improving protein digestion.
- An attempt should always be made to find an acceptable commercial food that will increase owner compliance with the dietary change and ensure a nutritionally adequate ration.
- Short term relief may be gained with fatty acids, antihistamines and steroids etc., but elimination of products from the diet is the only long term solution.
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*Corresponding author: Assistant Professor, Department of Veterinary Clinical Medicine, Veterinary College and Research Institute, Namakkal- 637 002, Tamil Nadu Veterinary and Animal Sciences University, Tamil Nadu, India, email: email@example.com
** Department of Veterinary Clinical Medicine, Veterinary College and Research Institute, Namakkal- 637 002, Tamil Nadu Veterinary and Animal Sciences University, Tamil Nadu, India.