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 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 testing². 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, tricyclic antidepressants and glucocorticoids. Withdrawal times of 2, 4 and 8 weeks have been suggested for topical, oral and long-acting injectable steroids respectively, although this may be diffcult in a very pruritic animal. Some animals require sedation for intradermal skin testing and xylazine and medetomidine have been shown not to affect results. Diazepam and acepromzine should not be used².

26-27 gauge needles are used to inject allergen intradermally. Histamine is used as a positive control, and isotonic saline as a negative. Approximately 0.05-1.0 ml solution is injected at each site, and after around 15 minues the test is read by scoring each allergen based on the size of the bleb.

 

Inflamed or infected skin makes IST difficult. Ideally, patients should be treated for their pyoderma or Malassezia dermatitis prior to testing.

 

Sedation is recommended for IST as testing is more easily performed. Sedatives that have been demonstrated to not affect test results include xylazine HCL, Medetomidine, and Tiletamine/zolazepam. Diazepam, oxymorphone, acepromazine and propofal may all adversely affect test results. The lateral thorax is routinely used for testing. The site is clipped with a #40 blade.

 

Intradermal injections are made with 26-27 g needles. Sharp needles ensure less bruising and easier injections. Positive (histamine phosphate 1:100,000) and negative (0.9% buffered saline) control injections are made to help ensure test accuracy. Injections are made utilizing approximately 0.05-1.0 ml solution. Injections are made based on "bleb" size. The injection blebs should be of approximately the same size at each injection site. Reactions are most commonly evaluated subjectively on a scale of 0-4 (compared to the positive and negative controls). Reactions are read at approximately 15 minutes. False positive reactions may occur with irritants, or allergens used at too high a concentration. False negatives may occur as well with drug interference, host factors, time of year, and improper technique.

===Biopsy===

===Biopsy===