chapter 11 Atopic Disease.......................................
DEFINITION/OVERVIEW
Atopic disease is a predisposition to develop allergic reactions to normally
innocuous substances, such as pollens (grasses, weeds, and trees), molds, house
dust mites, epithelial antigens, other environmental allergens, and occasionally
foods.Historically, atopic disease and atopy were considered synonymous.
Atopy by definition requires the presence of environmental allergen-specific IgE;
many patients with symptoms of atopic dermatitis do not have identifiable allergen-
specific IgE (designated as atopic-like dermatitis).Dogs and cats with adverse reactions to food may demonstrate symptoms indistin-
guishable from classic atopy.
The inclusive term “atopic disease” (AD) may be most appropriate.
ETIOLOGY/PATHOPHYSIOLOGY
Our understanding of the pathophysiology of AD is constantly changing and expand-
ing; each new study brings insight into the complexity of this disorder.
A brief explanation of current concepts, relating to cutaneous symptoms, is attempted
below for an understanding of treatment options addressing different aspects of the
etiology.Current Concept: Outside-Inside-Outside Theory
Defects in epidermal barrier function (outside) facilitate epidermal penetration of
allergens and microbes, increasing their exposure in genetically predisposed individ-
uals.Increased exposure produces sensitization (inside).
Sensitization and elicitation lead to reactions that include pruritus as well as exacer-
bating damage of the epidermis, furthering barrier dysfunction (outside).
Defects in epidermal barrier function are evidenced as:Decreases in and disorganization of lipids within the stratum corneum
Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Dermatology, Third Edition.
Karen Helton Rhodes and Alexander H. Werner.
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