9- Allergic skin Flashcards
Define allergy
a condition characterised by a hypersensitivity response to allergens
Common cause of pruritus, particularly in companion animals
What is the most common cause of allergy in cows
Insect bite hypersensitivity
Mite hypersensitivity
Define hypersensitivity
exaggerated response of immune system to an antigen
What are the key features of type 1 hypersensitivity
Cross-linking of IgE molecules on mast cell surface by allergen –> degranulation –> tissue inflammation
Occurs immediately
What are the key features of type 2 hypersensitivity
Destruction of target cell by effects of antibody (usually IgG or IgM) and complement pathway
What are the key features of type 3 hypersensitivity
Ab-Ag complexes
- form locally in tissue (if Ab in excess)
- circulate systemically (if Ag excess)
–> local or multisystemic inflammation
What are the key features of type 4 hypersensitivity
Sensitised mononuclear inflammatory cells (esp T lymphocytes, macrophages) release proinflammatory/regulatory cytokines
Define atopic dermatitis
allergic skin condition associated with hypersensitivity response to environmental +/or food allergens
What type of hypersensitivity is atopic dermatitis?
Type 1- IgE response
List 2 of the most common causes of allergy in dogs
environmental atopic dermatits
food-induced atopic dermatitis
flea allergic dermatitis
what type of hypersensitivity is sweet itch in horses
type 1 and 4 hypersensitivity to midge salivary proteins
Describe the clinical signs of equine atopic dermatitis
pruritis +/- urticaria (a raised, itchy rash that appears on the skin)
sometimes nodules (eosinophillic granulomas)
lesion distribtion poorly-definied
What are the cutaneous reaction patterns in cats
- Face, head, neck pruritus (FHN)
- Self-induced alopecia (SIA)
- Miliary dermatitis (MD)
(multiple 1-2mm papulo-crustous lesions) - Eosinophilic granuloma complex (EGC)
(eosinophilic granulomas/ulcers/plaques)
describe the clinical signs of feline food allergy
GI
conjunctivitis
resp signs
