Changes

===Other Tests===

===Other Tests===

Intradermal skin tests determine the ability of allergens injected intradermally to cause mast cell degranulation leading to a subsequent wheal and flare reaction. It is therefore a close approximation of the pathogenesis of atopic dermatitis, and is a useful tests for revealing specific allergens for use in immunotherapy. Aqueous allergens are used for testing and include such things as house dust mites, pollens, moulds, insects and epidermal antigens. These should be stored in the fridge to maintain potency, and allowed to reach room temperature before testing<sup2</sup>. Test results can be affected or inhibited by numerous factors such as medications, sedatives and stress. Drugs shown to affect intradermal skin testing include antihistamines, tricyclid antidepressants and glucocorticoids.

 

Intradermal skin tests (IST) detect the ability of allergens injected intradermally to cause mast cell degranulation leading to a subsequent wheal and flare reaction. Aqueous allergens are used for testing. Allergens are selected based upon the region in which the patient lives. Tree, weed, and grass pollens as well as molds, house dust mites, insects and epidermals should be included in the test. In theory, testing should be performed utilizing the highest concentration of extract that does not cause an irritant reaction. Recommended test strengths for allergens are as follows: 1000 PNU/ml for pollens, 1:50,000 W/V for house dust mites, 250-500 PNU for epidermals and 1000 PNU/ml for insects.

 

Aqueous allergen extracts lose potency over time, particularly when in their more dilute form for testing. Diluted allergens should not be kept for longer than 2 weeks. They should be stored at 4C. Prior to testing, allergens should be allowed to reach room temperature. Once testing is completed, allergens should be returned to the refrigerator as soon as possible.

 

Test results can be affected or inhibited by numerous factors: medications, sedatives, stress, etc.

 

Antihistamines: Hydroxyzine has been shown to inhibit skin test reactivity, and it is presumed that other antihistamines will have the same effect. A withdrawal period of 10 days is recommended, and longer for antihistamines with longer half-lives (ceterizine, etc).

 

Tricyclic Antidepressants: Histamine reactivity is affected by doxepin in people for up to 11 days.

Glucocorticoids: Withdrawal of topical glucocorticoids for 3 weeks has been suggested, oral glucocorticoids a minimum of 3 weeks, and repositol steroids for a minimum of 8 weeks. However, the optimal times have not definitively been established. Patients that have been receiving glucocorticoid therapy for extended periods of time may require a longer withdrawal period, and some dogs may have positive results with a shorter withdrawal period.

Glucocorticoids: Withdrawal of topical glucocorticoids for 3 weeks has been suggested, oral glucocorticoids a minimum of 3 weeks, and repositol steroids for a minimum of 8 weeks. However, the optimal times have not definitively been established. Patients that have been receiving glucocorticoid therapy for extended periods of time may require a longer withdrawal period, and some dogs may have positive results with a shorter withdrawal period.