Atopic dermatitis, also known as allergic inhalant dermatitis, has a ______ predisposition.
What are the major pathologic mechanisms associated with atopic dermatitis?
type I hypersensitivity and disruption/damage to the epidermal barrier
What is type I hypersensitivity mediated by?
IgE and subclasses of IgG
How does an animal become sensitized to an allergen?
An initial exposure to the antigen is required, then later exposure will lead to a reaction
What specific molecule plays a big role in pruritus due to atopic dermatitis?
On a cellular level, what has been found in atopic patients?
they have been shown to have a cellular defect that allows increased adherence of bacteria to keratinocytes leading to increased bacterial infections
What allergens are known to cause atopic dermatitis?
pollens, molds, house dust mites, epidermals (wool, feathers, horse, human), insects, and many others (like tobacco)
What allergens typically appear in the spring?
trees and molds
What allergens typically appear in the summer?
grasses, and some weeds
What allergens typically appear in the fall?
weeds and molds
What allergens typically appear in the winter?
indoor allergens (dust mites, molds)
What allergens are typically year-round?
indoor allergens and combinations of the seasonal ones
At what age does atopic dermatitis typicall present?
9 months - 3 years of age
What is the hallmark of atopy?
What are some signs of pruritus?
licking the feet, rubbing the fase, perineal pruritus, and generalized scratching
How do atopic lesions initally present?
mild: erythema, papules, and mild alopecia
What lesions are associated with chronic atopy?
lichenification, hyperpigmentation, and generalized alopecia
What areas are typically effected with atopy?
thin-skinned regions, such as the feet and between the toes, around the eyes, and in the axilla and inguinal regions
What is a common manifestation of atopy?
How may cats with allergic disease present?
they may have miliary dermatitis or other 'reaction patterns of cats' and generalized pruritus
What often perpetuates atopic dermatitis?
What secondary infections are commonly associated with atopic dermatitis?
superficial pyoderma and Malassezia dermatitis
What are secondary infections frequently the cause of?
apparent' treatment failure of atopics: so-called 'prednisone resistance'
Aside from secondary manifestations, otitis externa, and pruritus, what are some other clinical manifestations of allergy?
chronic anal sac inflammation and pruritus, acral lick dermatitis, and interdigital dermatitis
What are some diagnostic tools to diagnosing atopic dermatitis?
history, physical findings, dermatologic data base, allergy tests
What are the indications for allergy tests?
To confirm the diagnosis and to provide informtation for alternative therapy
What is intradermal skin testing?
Injection of known amounts of allergens intradermally and comparing the reaction to a positive (histamine) and negative control (saline)
What can be used for chemical restraint during intradermal skin testing?
only injalants, xylazine, dexdomitor, and some narcotis (no phenothiazines)
What is the technique for intraderma skin testing?
1. Injections are made in the lateral thoracolumbar area after gentle clipping 2. No skin preparation 3. Area can be marked with a felt-tipped pen 4. Injection of 0.05 ml of antigen intradermally with a 25-gauge needle
When do you read the results from intradermal skin testing?
Reactions are read at 0, 15, and 30 minutes