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Food allergy in canines: A review

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Amir Amin Sheikh

Sher-e-Kashmir University of Agricultural Sciences and Technology Jammu

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Journal of Entomology and Zoology Studies 2017; 5(6): 1522-1525

E-ISSN: 2320-7078

P-ISSN: 2349-6800

JEZS 2017; 5(6): 1522-1525

Received: 22-09-2017

Accepted: 24-10-2017

Rakshanda Bhagat

Division of Veterinary Medicine,

Sher-e-Kashmir University of

Agricultural Sciences and

Technology - Jammu (SKUAST-

J), R. S. Pura, Jammu and

Kashmir, India

Amir Amin Sheikh

Department of Veterinary

Physiology and Biochemistry,

College of Veterinary Sciences

and Animal Husbandry,

Jabalpur, Madhya Pradesh,

India

VS Wazir

Division of Veterinary Medicine,

Sher-e-Kashmir University of

Agricultural Sciences and

Technology - Jammu (SKUAST-

J), R. S. Pura, Jammu and

Kashmir, India

Aditya Mishra

Department of Veterinary

Physiology and Biochemistry,

College of Veterinary Sciences

and Animal Husbandry,

Jabalpur (M.P), India

Uttarani Maibam

Department of Veterinary

Physiology and Biochemistry,

International Institute of

Veterinary Education and

Research (IIVER), Rohtak,

Haryana, India

Correspondence

Amir Amin Sheikh

Department of Veterinary

Physiology and Biochemistry,

College of Veterinary Sciences

and Animal Husbandry,

Jabalpur, Madhya Pradesh,

India

Food allergy in canines: A review

Rakshanda Bhagat, Amir Amin Sheikh, VS Wazir, Aditya Mishra and

Uttarani Maibam

Abstract

Food allergy is an immunological response to the ingested allergen present in food like artificial food

additives, beef, canned foods, corn, cow milk, dairy products, dog foods, dog biscuits, eggs, fish, and

food preservatives, meat of different species including pork, mutton and horse meat, oat meal, potatoes,

rice and commonly occurs in dogs and cats. Among all canine species, Labrador and German shepherd

were found to be more prone to food allergy and symptoms are similar to other pruritic skin diseases.

These food allergies are broadly classified into two categories (1) IgE-mediated food allergy (2) non-IgE-

mediated food allergy. Diagnosis can be done by accurate clinical history, parental observations, and

laboratory tests: Skin scrapping, bacterial/fungal culture examination, thyroid test, fecal examination and

skin biopsy, allergic tests: Patch test, Skin Prick Test, Intra-dermal test and Radioallergosorbent test.

Management of these allergies can be done by antihistaminics like Hydroxyzine and Chlorpheniramine,

antibiotics like Cephalexin, Enrofloxacin, antifungals like Ketoconazole, Griseofulvin, Amphotericin-B

and glucocorticoids like Prednisolone, Methyl prednisolone.

Keywords: Food allergy, IgE mediated, non-IgE mediated, Patch test

1. Introduction

Adverse reactions in dogs and cats to allergens present in food is the commonest form of

hypersensitivity and frequently reported to occur next to flea allergic dermatitis and atopic

dermatitis. It is defined as the clinically abnormal exaggerated immunological

reaction/response to the ingested allergen present in food as described by National Institute of

Allergy and Infectious Diseases, 2011. Alternatively the food allergy and food/dietary

hypersensitivity are used interchangeably. All food reactions are not considered as food

allergies [1]. Adverse reactions to food account for 10-20% of all the skin problems been

reported till date [2]. It is associated mostly with the protein component present in the food that

elicits an immunological response that is capable of bridging the two molecules of IgE thereby

triggering degranulation in the mast cells thus causing the release of mediators of

inflammation [3].

2. Classification

Broadly untoward reactions to food are classified on the basis of response elicited into two

types: immunological and non-immunological. Food allergy/food anaphylaxis is categorized

under immunological response which may be IgE mediated or non IgE-mediated. Mostly, it is

of type I (immediate) hypersensitivity reactions, mediated by immunoglobulin E (IgE) but in

some cases both types III and IV hypersensitivity may also be involved. Glycoproteins with a

molecular weight ranging between 10 and 60 kilo Daltons are considered as the antigens which

can cause reaction within minutes to hours, days and can even take longer periods to get

sensitized to present clinical manifestations. Whereas food poisoning, food intolerance and

dietary indiscretion are classified under non-immunological response. Food intolerance is

further subdivided namely reaction due to pharmacological active ingredient, reaction due to

metabolism of certain ingredients, food idiosyncrasy and pseudo allergy [4]. Pharmacological

reaction to food is initiated by stimulation of response to certain pharmacological active agent

present in food having drug like action. Mostly response is seen in intestine causing motility

disorders manifested as diarrhea. An example is monosodium glutamate used as a flavour

enhancer in dogs. In addition, physiological compounds like casomorphins also reported to

alter the gut motility and manipulation of the omega-3 and omega-6 ratio in food causes

alteration of prostaglandin production [5].

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Journal of Entomology and Zoology Studies

Metabolic reaction to food is due to genetic error of

metabolism that is inborn in nature. Chronic hepatitis in

Doberman dogs is a classical example. Inability to excrete

copper causes copper toxicosis leading to chronic hepatitis in

these dogs [6]. Indigestible or unabsorbed products (lactulose),

or deficiency of certain enzymes (lactase) can result in a

metabolic food reaction [7].

Food idiosyncrasy is mostly mechanical in nature as occurs

due to less fibre in the diet or the presence of certain

indigestible (bones) products [8]. In contrast production of

histamine (ingestion of Tuna fish and Shell fish) which is

responsible for mast cell degranulation is categorized under

pseudo allergy. [2]. defined Canine food allergy

/hypersensitivity as a non-seasonal pruritus (regional or

generalized) with involvement of ears, feet, inguinal or

axillary areas, face, neck, and perineum. Erythema with a

papular rash including alopecia, excoriations, scales, crusts

and hyperpigmentation of the affected skin areas. It is very

difficult for the clinician to distinguish atopic dermatitis and

food allergy based on clinical signs although seasonality of

occurrence, response to steroid therapy can give useful hints.

In Atopic dermatitis there is a genetic predisposition of

developing hypersensitivity reactions (type 1) to substances

present in environment such as dust, pollens etc.

3. Predisposition, contributing factors and etiology

3.1 Predisposition and contributing factors

Food allergy has no age predisposition [9], no sex predilection

in dogs (Chesney, 2002) with no seasonality of occurrence

[10]. Labrador and German shepherd were found to be more

prone to food allergy [2] although any breed including mixed

breeds may be affected. [11] Reported 33%, 51% and 16%

incidence in < 1 year, 1-5 years and 5-11 years of dogs

respectively. Protein and carbohydrate source in pet food,

certain foods and food ingredients, any disease that increases

intestinal permeability (e.g. viral enteritis), selective IgA

deficiency, poorly digestible protein and other allergic disease

[12].

3.2 Etiology

The offending antigen is usually a basic food ingredient in the

animal’s diet responsible for the food allergy. A wide range of

dietary ingredients responsible for food hypersensitivity

includes artificial food additives, beef, canned foods, corn,

cow milk, dairy products, dog foods, dog biscuits, eggs, fish,

food preservatives, meats of different species including pork,

mutton and horse meat, oat meal, potatoes, rice flour, soy,

wheat, kidney beans. A prospective study was conducted in

25 dogs to characterize specific food ingredients causing

adverse reactions [13]. Single-ingredient stimulation trials were

conducted with beef, chicken, chicken eggs, cow milk, wheat,

soy and corn. Among all the ingredients, beef and soy were

found to cause most cutaneous adverse reactions, although all

ingredients induced clinical signs in at least one dog. 36%

percent of dogs reacted to one protein and the mean number

of suspected allergens per dog was 2.4. Recently in 15

different experimental studies, representing 278 dogs from

different continents were assessed to check ingredients that

are commonly associated with adverse food reactions. These

experimental studies showed beef, dairy products and wheat

accounted for 69% of reported cases where as lamb, chicken

egg, chicken and soy accounted for 25% of the dogs. In 10

experimental studies conducted on 56 cats, beef, dairy

products and fish were associated with food reactions in 80%

of the animals [12]. In one beef allergic dog, bovine serum

albumin was found to be the target of anti-beef IgE [14]. A

study carried on 10 dogs, it was found that major allergen in

cow’s milk that cause allergic reactions is bovine IgG and

because of high homology of bovine IgG with ovine

immunoglobulins it can be a possible source of cross-

reactivity with beef and lamb (similar to meat allergy in

humans). Cow’s milk is a wholesome food containing about

20 protein components [15]. The milk-protein fractions are thus

subdivided into casein proteins (78-86%) and whey protein

(14-24%). β-lactoglobulin is the most allergic component,

followed by casein, lactalbumin, and bovine serum albumin.

Dogs that were allergic to cow’s milk could not eat cheese

and vice versa [16]. Hidden allergens can also be a problem

with food allergies including a number of oils such as corn

and soy. A milk protein (Sodium caseinate), is often added to

improve the packaging qualities in canned tuna is also

responsible for the allergic reaction.

4. Pathogenesis

A food allergy arises when there is a reproducible reaction to

a specific food or food additive with a proven immunological

basis. There are two types: an IgE mediated and a non-IgE-

mediated response.

4.1 IgE-mediated food allergy

It is commonly believed that food allergy is, in most cases, an

IgE-mediated type 1 reaction (Gell & Coombs classification)

[7]. However, it is documented and reported to occur by other

types also including notably type iii and iv [4]. In type 1

hypersensitivity reaction, specific allergen triggers the IgE

sensitized mast cells which causes release its pharmacological

mediators thus setting in the process of inflammation. Clinical

signs mostly depend on system/tissue in which reaction

occurs. It may include dermatological, respiratory,

gastrointestinal signs, or a combination. Several reasons are

responsible for how an allergen can induce abnormal response

in food allergy.

Firstly, the allergen may have the ability to penetrate the

physiological mucosal barrier. The components of this barrier

include digestive enzymes, gastric acidity, peristalsis, the

surface mucus, enterocyte tight junctions, and the

immunological barrier of intraluminal IgA. After penetrating

the mucosal barrier, the allergen will interact with

gastrointestinal associated lymphoid tissue (galt). The galt is

formed by the Peyer’s patches, diffuse lymphoid tissue in the

lamina propria, enterocytes, and intraepithelial lymphocytes

[4]. The immune response in the galt usually leads to a Th2-

mediated response in which the cytokines interleukin IL-4 and

IL-5 stimulate IgA production and immune responses

involving mast cells and eosinophils. In a type i reaction, the

antigen is presented by an antigen-presenting cell to a Th2

cell, which then produces IL-4 and IL-10. These cytokines

stimulate B cell proliferation and induce IgE production. The

resultant IgE binds to mast cells and sensitizes them. If the

allergen reaches the sensitized mast cell, it releases histamine,

proteases, as well as several leukotrienes and prostaglandins.

IL-4 produced by Th2 cells influences, among others, tnf-α

and tnf-β production [17].

Normally, an antigen will induce oral tolerance, which is an

active response and is designed to limit the unnecessary and

wasteful activity of galt in response to ‘harmless’ luminal

antigens, such as those from endogenous microbiota. If, for

whatever reason, this normal tolerance is abolished, the

antigen induces an inappropriate immune response to

endogenous flora (resulting in Inflammatory Bowel Disease)

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Journal of Entomology and Zoology Studies

or, in the case of food allergens, food allergy [4]. The food

allergens that trigger such an abnormal response are usually

soluble protein or glycoproteins resistant to degeneration [4].

In dogs, common allergens are derived from beef, chicken,

milk, eggs, corn, wheat, and soy [18]; in contrast, reactions in

cats are more commonly to dairy and fish proteins. As such,

no particular protein is especially ‘allergenic’. Animals are

more likely to respond adversely to dietary components to

which they are commonly exposed. Factors that contribute to

food allergy either interfere with the normal mucosal barrier

(viruses, bacteria, parasites, toxins, etc), lead to an abnormal

presentation of the antigen to the galt, or cause deregulation

of the galt [4].

4.2 Non-IgE-mediated food allergy:

Non-IgE-mediated anaphylaxis or gluten-sensitivity most

likely involves a type iii or iv immunological reaction

although some believe it to be more an intolerance than

immunologic of nature. In gluten-sensitivity, gliadens, one of

the four gluten proteins, induce a non-IgE-mediated mast cell

response as in IgE-mediated food allergy. Gluten sensitivity

was demonstrated in a single cohort of young Irish setters [19].

Hence, the opinion that gluten should be avoided in all cases

of gastrointestinal diseases (or in all dog foods) is flawed.

5. Clinical Signs

Reactions to ingested food components can affect many body

systems and can produce signs involving the skin,

gastrointestinal tract, respiratory tract and central nervous

system. Dermatological signs include pruritus, erythma,

papular eruptions are common and often seen with a

secondary staphylococcal folliculitis infection, otitis externa

(unilateral or bilateral), Urticaria. Occasionally, dogs will be

non-pruritic and exhibit only seborrhoe [20]. Self inflicted

trauma in pruritic cases resulting in excoriation, alopecia and

secondary superficial pyoderma are also noticed.

5.1 Food anaphylaxis is an acute response to ingestion of

food or food additives resulting in various systemic

consequences

 Angioedema or facioconjunctival edema [10].

 Angioedema is typically manifested by large edematous

swellings of the lips, face, eyelids, ears, conjunctiva

and/or tongue, with or without pruritus [10].

 These reactions usually occur within minutes of allergen

exposure and generally subside after one to two hours

 1/4th of dogs with AFR had lesions only in the region [21].

 Adverse food reactions should always be with pruritic,

unilateral or bilateral otitis externa, it may accompanied

by secondary bacterial or Malassezia infections [10].

Other presentations of food allergy include recurrent

superficial pyoderma, pruritic papular eruptions over the trunk

and head [2].Adverse food reactions concurrent to flea-allergic

or atopic dermatitis accounting for 20% to 30% or more of

dogs has been documented [22]. Concurrent GIT signs

(vomiting, diarrhea, frequent defecation, colitis etc) were seen

to occur in 10-15% dogs with skin infections caused by an

adverse reaction to food [23]. Neurological signs, such as

seizures, malaise have been reported [24].Although asthma and

other respiratory signs have also been reported, these clinical

signs are rare [3].

Diagnosis and management

6.1 Diagnosis can be done by

a. Accurate clinical history

b. Parental observations: Clinical symptoms, physical

examination

c. Laboratory tests: Skin scrapping, bacterial/fungal culture

examination, thyroid test, fecal examination and skin

biopsy

d. Allergic tests: Patch test, Scratch tests (Skin Prick Test),

Intra-dermal test and RAST (Radioallergosorbent test).

e. Dietary investigation in the form of elimination diets and

test meals

f. Diet selection: Limited antigen diet, in common use, is of

3 types: Home-cooked diets, commercially available

novel protein diets, Hydrolyzed protein diet.

g. Challenge diet: Dog should be challenged with old diet.

If symptoms do not recur with challenge: improvement

would have been coincidental & if symptoms do recur,

the diet should be switched back to the elimination diet.

h. Gastroscopic food sensitivity testing (GFST)

i. Endoscopic observation of gastric mucosal reaction

following exposure to pure food extracts [25].

h. Colonoscopic food sensitivity test (CFST)

 Allergens injected directly into the mucosa of the colon

 Results observed as wheal and flare reactions.

5.2 Management

5.2.1 Antihistaminic drugs: They counteract the release of

histamine from the mast cells, which is the source of the

itching. Some of the common antihistaminics used are:

Diphenhydramine hydrochloride @ 2mg/kg B.W,

Hydroxazine @ 2.2 mg/kg B.W, Chlorpheneramine @4-8

mg/kg B.W

5.2.2 Antibacterial drugs: Some dogs scratch so severely that

they cause a secondary bacterial infection of the skin called

pyoderma (Staphylococcus intermedius), which intensifies the

itching. Antibiotics that work best for pyoderma include:

Cephalexin @ 22 mg/kg B.W, Enrofloxacin @ 2.5 -5 mg/kg

B.W, Erythromycin @ 10 mg/kg B.W, Clavulanic acid +

Amoxycillin combination @ 13.5 mg/kg BW. The dog should

be bathed with shampoo that will help in controlling the skin

infection, eg. Benzoyl peroxide or chlorhexidine containing

shampoo.

5.2.3 Antifungal drugs: Secondary fungal infections can

occur, especially when the feet are licked constantly. The

commonly used antifungal agents include: Ketoconazole @ 5-

10 mg/kg B.W, Griseofulvin @ 25 mg/kg B.W,

Amphotericin-B @ 0.5 mg/kg B.W. Bathing the dog with a

shampoo containing ketoconazole and chlorhexidine.

5.2.4 T-cell inhibitor: Cyclosporine @ 5mg/kg B.W,

Tacrolimus @ 2 mg/kg B.W

5.2.4 Glucocorticoids: Prednisolone @ 2-4 mg/kg B.W,

Methyl prednisolone @ 1-2 mg/kg B.W

5.2.5 Food supplements: Feed diets balanced with vitamin,

mineral and fatty acid supplements e.g. omega-3 and omega-

6. Conclusion

Food hypersensitivity is a relatively common cause of allergic

skin disease of dogs Symptoms are similar to other pruritic

skin diseases, a methodical approach is required to establish a

definitive diagnosis. Secondary infections of the skin and ears

are common with food allergy, particularly in the dog. These

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Journal of Entomology and Zoology Studies

infections must be resolved prior to completion of an

elimination diet. An 8–12 week elimination diet is the only

reliable way to diagnose food allergy in the dog and cat. If

improvement or resolution of symptoms is seen, the diagnosis

can be confirmed by provocative challenge with the former

diet. Long term management of food allergy in the dog

requires avoidance of the offending allergen(s). The

investigation and diagnosis of food hypersensitivity are

laborious and frustrating.

7. Acknowledgements

The authors would like to acknowledge Dr. V.S Wazir,

Associate Professor, Division of Veterinary Medicine, F.V.Sc

& A.H, R.S. Pura, Jammu for providing me all the invaluable

insights and regular encouragement throughout the whole

study.

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