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Food Allergy, Dermatologic 345

Advanced or Confirmatory Testing PROGNOSIS & OUTCOME Technical Tips
• Skin biopsy and histopathologic evaluation: • These entities are incurable, genetically based Discuss sun protection with owners of dogs
VetBooks.ir clumping in follicular basal cells, hair bulbs, • Affected dogs are otherwise healthy, with the pigmented. Diseases and Disorders
dilated and cystic hair follicles with melanin
suffering alopecia, particularly if skin is lightly
dermatoses.
hair shafts, follicular lumen in CDA and
BHFD
• Any diagnostic procedure necessary to rule exception of secondary pyoderma in CDA. SUGGESTED READING
Cerundolo R, et al: Breed specific hair-cycle abnor-
out other differential diagnoses (p. 1091) PEARLS & CONSIDERATIONS malities. In Mecklenburg L, et al, editors: Hair loss
disorders in domestic animals, Ames, IA, 2009,
TREATMENT Comments Wiley-Blackwell, pp 169-175.
• The early onset, color link (CDA, BHFD), AUTHOR & EDITOR: Manon Paradis, DMV, MVSc,
Treatment Overview and/or breed predisposition make the DACVD
The main goals are to attempt hair regrowth and diagnosis straightforward in many cases.
control secondary bacterial folliculitis, which • The main impact of these disorders is cos-
is commonly seen in CDA. metic rather than medical, unless secondary
infection or sunburn occurs.
Acute General Treatment
Anecdotal evidence exists for the efficacy of
melatonin (3-6 mg/DOG PO q 8-12h for 1-2
months) to stimulate hair growth in CDA.

Food Allergy, Dermatologic Bonus Material Client Education
Sheet
Online

BASIC INFORMATION deficiency, age (<1 year), and concurrent allergic ○ Rare primary lesions, such as urticaria, or
disease. angioedema may occur.
Definition • Cats
A well-recognized, abnormal response to an GEOGRAPHY AND SEASONALITY ○ Lesion/pruritus distribution: often cen-
ingested food or food additive that produces Nonseasonal tered on the head and neck but may be
clinical signs affecting the skin, most commonly generalized
pruritus ASSOCIATED DISORDERS ○ Manifestations may consist of general-
• 20%-30% of cases may have concurrent ized pruritus without lesions; miliary
Synonyms atopic dermatitis or flea allergy dermatitis. dermatitis; pruritus with self-trauma
The preferred term is cutaneous adverse food • 20%-25% of cases may have concurrent centered around the head, neck, and
reaction (CAFR). The terms food allergy or gastrointestinal (GI) signs (e.g., vomiting, ears; self-induced alopecia; or lesions of
food hypersensitivity are often incorrectly used diarrhea, flatulence). the eosinophilic granuloma complex.
synonymously with adverse food reaction. These • Secondary skin infections with bacteria and
terms more accurately refer specifically to the yeast are common. Etiology and Pathophysiology
subcategory of adverse food reactions that have Clinical Presentation • A variety of causes are proposed.
an immunologic basis. The term food intolerance, • The majority are attributed to food aller-
also encompassed within CAFR, is reserved HISTORY, CHIEF COMPLAINT gies; however, immunologic tests are rarely
for the subcategory of adverse food reactions • The chief complaint is nonseasonal pruritus, performed to confirm this suspicion.
without an immunologic basis and includes recurrent pyoderma, or otitis externa. • Common food allergens in dogs include beef,
metabolic food reactions, food poisoning, food • There may be a history of a poor response dairy products, chicken, wheat, and lamb.
idiosyncrasies, and pharmacologic reactions to to glucocorticoid therapy. • Common food allergens in cats include beef,
food. • Adverse food reactions with an immunologic fish, and chicken.
component usually develop after prolonged • Food allergies are thought to be the result of
Epidemiology exposure to a food allergen, whereas food primarily a type I hypersensitivity reaction,
SPECIES, AGE, SEX intolerance may occur after a single expo- although type III and IV reactions have also
• Dogs: age of onset from 4 months to 14 sure because immune mechanisms are not been proposed.
years (mean, 2.2 years; 77% develop signs involved. • Several host defenses exist to prevent
by 3 years) absorption of intact allergens from the GI
• Cats: from 6 months to 12 years (mean, 4 PHYSICAL EXAM FINDINGS tract, including effective digestion, intestinal
years; 52% develop signs by 3 years) • No specific pattern of skin lesions exists. peristalsis, an intact intestinal mucous layer,
• Dogs tight junctions between mucosal cells, and
GENETICS, BREED PREDISPOSITION ○ Lesion/pruritus distribution: feet, face, mucosal IgA. The small amounts of food
Dogs and cats: no strong breed predisposition ears, axillae, perianal region, inguinal proteins that do cross the intestinal mucosa
region, and rump activate suppressor T cells and stimulate an
RISK FACTORS ○ There may be pruritus without lesions or immune response in the gut-associated
Risk factors include certain foods or food lesions secondary to infections and pruritus lymphoid tissue that leads to tolerance. A
ingredients, poorly digestible proteins, any such as papules, pustules, erythema, excoria- defect in any of these defense mechanisms
disease that increases intestinal mucosal per- tions, lichenification, alopecia, scales, crust, may lead to sensitization of the immune
meability, selective immunoglobulin A (IgA) and acute moist pyotraumatic dermatitis. system and development of a food allergy.

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