ISSN 2398-2969      

Skin: food hypersensitivity

icanis

Synonym(s): Dietary intolerance, Food hypersensitivity


Introduction

  • Cause: sensitivity to components of the diet resulting in skin disease.
  • Signs: there may be concurrent gastrointestinal signs and this may be the reason for advice being sought.
  • Can mimic any dermatosis, but often clinically indistinguishable from atopy.
  • Diagnosis: history, clinical signs, histopathology, response to treatment.
  • Treatment: hypoallergenic diet.
  • Prognosis: excellent if allergens identified and eliminated.
Follow the diagnostic tree for Suspected food allergy in dogs.

Pathogenesis

Etiology

  • Unknown.
  • Common foodstuffs documented to cause disease: beef, dairy products, chicken, wheat, eggs, corn, soya - related to prevalence of food stuffs in diet.

What are roles of food-specific IgE and IgG antibodies in food allergy?

  • IgE antibody:
    • The role of the allergen-specific IgE antibody in the immunopathology of allergic disease has been well characterized (Halliwell 1992).
    • Essentially, allergen-specific IgE antibody is able to sensitize mast cells, dispersed in the connective tissue in the skin or gut, through binding a surface receptor molecule.
    • On repeat exposure, allergen in direct contact with a sensitized mast cell may cross-link the surface bound IgE molecules. This event results in the release of mast cell-derived inflammatory mediators such as histamine, proteases and prostaglandins.
    • The pharmacological effects of these mediators on local tissue result in inflammation and the clinical sings of food allergy.
  • IgG antibody:
    • The role of food allergen-specific IgG in allergic disease has yet to be proven conclusively.
    • Food allergen-specific IgG antibodies can be detected in healthy individuals and are regarded by many as irrelevant to food allergy.
    • However, high serum concentrations of food-specific IgG have been shown to be potentially useful diagnostic indicators of delayed food allergy in humans.

Predisposing factors

General

  • Underlying gastrointestinal pathology.

Specific

  • Gluten sensitive enteropathy Gluten-sensitive enteropathy.
  • IBD Inflammatory bowel disease: overview.
  • Eosinophilic colitis.
  • Lymphocytic-plasmocytic colitis.
  • In most normal dogs effective mechanisms suppress inappropriate immune responses to harmless dietary allergens resulting in tolerance.
  • When this system breaks down immune responses may be mounted.

Pathophysiology

  • An uncommon disease.
  • True food allergy does exist but is clinically indistinguishable from non-immunologic food intolerance.
  • Diagnosis of adverse response to food usually confirmed through response to exclusion diet.
  • Reactions may be immediate (1-2 hours) or delayed (several days).
  • Food allergies affecting skin are often caused by a single food whereas multiple food allergies are more common in gastrointestinal disease (Guilford 1994).
  • Very little known about pathophysiology of food allergy. Most commonly accepted theory is Type I hypersensitivity.
  • Anaphylactoid reaction due to presence of histamine may be one mechanism.
  • Food allergy response in dogs is typically delayed (Rosser 1993).
  • Antigenic exposure gives rise to histamine-releasing factors which remain active some time after antigen is removed. This may explain the lag between introduction of a hypoallergenic diet and clinical improvement.
  • Allergic response may only become apparent when immunological activity threshold is breached, allergic breakthrough.
  • This is when a small increase in allergen load may provoke an allergic response, similarly removal of exposure to one of inciting allergens may be sufficient to produce clinical improvement.

Timecourse

  • Food sensitivities may occur immediately or may take months/years to develop ( >70% cases have been fed offending diet for more than 2 years).

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Ellwood C M & Garden O A (1999) Gastrointestinal immunity in health and disease. Vet Clin North Am Small Anim Pract 29 (2), 471-500 PubMed.
  • Hill P (1999) Diagnosing cutaneous food allergies in dogs and cats - practical considerations. In Practice 21 (6), 287-294 VetMedResource.
  • White S D (1998) Food allergy in dogs. Comp Cont Ed Prac Vet 20 (3), 261-269 VetMedResource.
  • Paterson S (1995) Food hypersensitivity in 20 dogs with skin and gastrointestinal signs. JSAP 36 (12), 529-534 PubMed.
  • Simpson J W (1995) Management of colonic disease in the dog. Waltham Focus 5, 17-22.
  • Fadok V A (1994) Diagnosing and managing the food-allergic dog. Comp Cont Ed Prac Vet 16 (12), 1541-1544 VetMedResource.
  • Halliwell R E W (1993) The serological diagnosis of IgE-mediated allergic disease in domestic animals. J Clin Immunoassay 16 (2), 103-108 VetMedResource.
  • Rosser E J (1993) Diagnosis of food allergy in dogs. JAVMA 203 (2), 259-262 PubMed.
  • Halliwell R E W (1992) Management of dietary hypersensitivity in the dog. JSAP 33 (4), 156-160 VetMedResource.
  • Kunkle G & Horner S (1992) Validity of skin testing for diagnosis of food allergy in dogs. JAVMA 200 (5), 677-680 PubMed.
  • Jeffers J G, Shanley K J & Meyer E K (1991) Diagnostic testing of dogs for food hypersensitivity. JAVMA 198 (2), 245-250 PubMed.
  • Scott D W (1978) Immunologic skin disorders of the dog and cat. Vet Clin North Am (4), 641-664 PubMed.

Other sources of information

  • Brostoff J & Hall A (1996) In: Immunology. 4th edn. Roti I, Brostoff J & Male D (eds). D Mosby, London. pp 15.
  • Wills J M & Halliwell R E W (1994) Dietary Sensitivity. In: The Waltham Book of Clinical Nutrition of the Dog and Cat. pp 167-188.
  • Reedy L M & Miller W H (1989) Allergic skin diseases of Dogs and Cats. W B Saunders, Philadelphia. pp 147-159.

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