Allergy Testing

Why should my pet have this test?

Many patients with atopic dermatitis (skin allergies) have high levels of an antibody called immunoglobulin E (IgE) in their blood. This IgE develops as a result of exposure to specific antigens or “allergens” in the pet's environment, such as pollens or dust mites. Each time your pet is re-exposed to the offending allergen, their IgE recognizes it and triggers the widespread allergic response (inflammation) that ultimately leads to the redness, itch and infection we see clinically. As pets age, they often develop IgE to additional allergens and their clinical signs become more severe and year-round.

What is Immunotherapy?

Immunotherapy (e.g. allergy shots or drops) is a treatment by which we identify which allergens your pet has IgE towards and administer tiny amounts of these allergens as drops under the tongue or as an under-the-skin injection. These drops/shots are given in gradually increasing amounts in order to train your pet’s immune system to tolerate the allergens, thus blunting the severity of the response when they are encountered in real life.

Immunotherapy reduces the severity of the allergic skin disease over time, while often reducing the allergic patient`s reliance on symptom-relieving drugs. It is drug-free and very-well tolerated. Approximately 90% of patients see a response to treatment, 60-70% of whom improve by approximately 60-70%. Most patients require immunotherapy treatment for the duration of their life in order to receive the full-benefit.

Successful immunotherapy beginswith allergy testing. These tests do not diagnose atopic dermatitis, but are to be used after a diagnosis has been made inorder to identify which allergens to include in an immunotherapy treatment. Most, but not all, allergic patients have positive reactions on allergy tests.

What types of tests do you use?

There are two types of tests: Intradermal allergy tests (skin prick test) identify reactions to allergens by injecting very small amounts directly into the skin, while serum allergy tests (blood test) measure levels of circulating allergen-specific IgE antibodies in your pet’s blood.

Which test is better?

Neither skin testing nor blood testing is consistently better and each has its pros/cons. For many patients, the results of either test would be comparable, but for others, one or the other may be more revealing or sensitive. Unfortunately, we cannot know in advance which one will be best for each patient. Sometimes, other factors can influence which test is best for your pet. For example, brachycephalic breeds (bulldogs, pugs) may require general anesthesia or increased monitoring for skin prick tests, thus a blood test may be advised initially.

There are numerous factors that veterinary dermatologists consider when selecting the most appropriate test, including the condition of the skin, the overall health of the patient, the ability to withdraw certain medications (see below),the time of year, and even the species being tested. In many cases, combining the two tests gives the best results.

Please note that we do not recommend or perform intradermal or serum tests forfood allergens. If food allergy is suspected, an elimination diet trial is the only effective method to rule it in or out.

What is the protocol?

For the serum allergy test, a blood sample is taken from your pet and submitted to a specific reference laboratory. It typically takes 2-3 weeks to receive the report. Though this form of testing is less expensive than an intradermal test, there is a higher chance of receiving “all-negative” results, as some allergic patients do not have as much IgE in their blood as they do in their skin. In that event, a skin test will likely be required.

The intradermal allergy test is a specialized procedure typically performed by veterinary dermatologists. The patient is first sedated in order to avoid any discomfort. A rectangular area of hair is clipped on the side of the chest. Small dots are drawn on the skin, after which the skin is injected with very small amounts of approximately 50+ of the most common environmental allergens. Our panel includes house dust mites, storage mites, numerous pollens (trees, grasses and weeds), flea, cockroach, mosquito, and yeast, among others. Histamine and saline are used for positive and negative controls.

Within 15-20 minutes, a small “hive” (redness and swelling) becomes evident at the site of any positive reactions (as well as at the positive control). The dermatologist grades each reaction individually and then makes a determination as to which allergens should be included in your pets immunotherapy formula.

  • The side of the chest will be clipped. Please plan accordingly if the patient is to participate in a show.
  • NO FOOD after 10pm the night before your appointment. Water is allowed.
  • Examine the chart below to ensure that your pet is not currently receiving any medications that may interfere with INTRADERMAL testing.

Long-acting injectable steroids:
Dexamethasone, Depo-Medrol, Triamcinolone

6-8 Weeks

Oral steroids:
Prednisone, prednisolone, Temaril-P,dexamethasone, triamcinolone etc.

21 Days

Steroidal topical skin, ear, and eye medications: Mometamax, Surolan, Otipak, Tresaderm, Otomax, Posatex, Osurnia, Panolog, Mometasone, Gentaspray, Cortisoothe shampoo, Dermacool HC, Malacetic Wipes HC, prednisolone eye drops, etc. *Ask if unsure*

14 Days

Certain oral medications (antihistamines, some tranquilizers):
Amitriptyline, Zyrtec (cetirizine), diphenhydramine (Benadryl), hydroxyzine (Atarax), chlorpheniramine (Chlor-Tripolon, Novo-Pheniram), clemastine (Tavist), clomipramine (Clomicalm), acepromazine (Acevet, Atravet)

7 Days

Do not discontinue any medications without consulting your primary care veterinarian first, in order to safely follow the suggested drug withdrawal times above. If drug withdrawal is not possible, a dermatology consultation is still a valuable option. In many patients, we can alter the drug regimen to allow testing at a later date.

The following medications DO NOT need to be discontinued:

Cyclosporine (Atopica), oclacitinib (Apoquel), lokivetmab (Cytopoint), essential fatty acids (fish oils, other oils), topical tacrolimus (Protopic), NSAIDS (Carprofen, Metacam, Rimadyl, Deramaxx, Previcox), antibiotics (cephalexin etc.), antifungals (ketoconazole, etc.), pentoxifylline, subcutaneous immunotherapy (allergy shots), sublingual immunotherapy (allergy drops), most ear cleaners, flea medications, insect repellants, thyroid / heart / antiseizure medications, glucosamine, chondroitin sulfate, all other medications/supplements.

Questions about these guidelines or testing in general? Please do not hesitate to call or email us.

Pet Dermatology Center
18 S Letitia Street
Philadelphia, PA 19106
P. (267) 427 - 2806

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