Ovc.uoguelph.ca

Ontario Veterinary College
Health Sciences Centre

Allergy Testing Instructions for Dogs, Cats and Horses
Allergy tests for atopic dermatitis and insect bite hypersensitivity

Atopic dermatitis in dogs/cats/horses and insect bite hypersensitivity in horses are common allergic
skin diseases associated with immunoglobulin E (IgE) antibodies to environmental allergens and
insect saliva.
Allergic patients suffering from these chronic skin conditions often benefit from allergy shots
(immunotherapy). Immunotherapy is a process in which offending allergens are injected
subcutaneously in gradually increasing amounts, inducing tolerance. The main benefit of
immunotherapy is its ability to reduce the severity of the allergic skin disease, and thereby reduce the
allergic patient`s reliance on symptom-relieving drugs.
Successful immunotherapy begins with allergy tests. These tests do not diagnose a patient as having
an allergic dermatitis, but rather identify offending environmental allergens or insects. Most, but not
all, allergic patients have positive reactions on allergy tests. Two types of allergy tests are used:
intradermal allergy tests identify reactions to allergens injected directly into the skin (see below), while
serum allergy tests measure circulating allergen-specific IgE antibodies.
Which test is better? Each test has certain advantages and disadvantages, and for each patient, one
test may be the more appropriate one. Factors veterinary dermatologists consider in selecting the
most appropriate test include 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 of the patient who is
to be tested for allergies. In many cases, combining the two tests gives the best results.

Important note: We do not offer intradermal or serum tests for food antigens as these tests are
not reliable for the diagnosis of food allergies in veterinary medicine.
Intradermal allergy test protocol

The intradermal allergy test is the procedure veterinary
dermatologists perform most often to identify offending allergens.
The patient is first sedated in order to avoid any discomfort.
A rectangular area of hair is clipped on the side of the chest in
dogs and cats, or the side of the neck in horses. Within a grid
layout, or nearby small dots drawn on the skin, the skin is injected
with small amounts of approximately 48 environmental allergens.
This panel includes house dust mites, storage mites, pollens
(trees, grasses and weeds), insects, fleas and molds.
Within 15-25 minutes, redness and swelling is evident at the site
of positive reactions. With the allergy test(s) complete, a
determination will be made whether or not immunotherapy and/or
allergen avoidance are appropriate. In horses, the test area needs
to be examined a second time, 4 hours after the initial allergen
injections.

451250 March2013
Guidelines for Intradermal Allergy Tests
Intradermal allergy testing is a delicate procedure, so it is helpful to adhere to the following guidelines:
1. Females cannot be skin tested if in heat, pregnant or in false pregnancy. 2. The chest or the neck will be clipped. Please plan accordingly if the patient is to participate in a show. 3. If the patient’s allergy is seasonal, which means it is strictly limited to or worsens during spring, summer or fall, it is best to schedule testing from August to November. 4. Bring your dog or cat fasted. Since sedation is required, please do not feed your pet at least 6 hours prior to the scheduled appointment. Drinking water is allowed. This precaution is not necessary in horses. 5. Ensure that the patient is not currently on anti-allergic medications or other medications that may cause The following withdrawal times (based on the most recent evidence-based guidelines published in our
specialty’s peer-reviewed journal) are recommended:
a. Long-acting injectable steroids Depo-Medrol, methylprednisolone acetate
b. Oral steroids Prednisone, prednisolone, Vanectyl-P, dexamethasone, triamcinolone
c. Steroidal topical skin, ear and eye medications
Aurizon, Surolan, Canaural, Tresaderm, Otomax, Mometamax, Synotic, Topagen,
Cortavance, Fuciderm, hydrocortisone cream, Cortisoothe shampoo, Dermacool HC,
Malacetic Wipes HC, Burow’s HC, BNPH, prednisolone for the eye etc.
d. Oral antihistamines and some tranquilizer medications
Amitriptyline, diphenhydramine (Benadryl), hydroxyzine (Atarax), cetirizine (Reactine),
chlorpheniramine (Chlor-Tripolon, Novo-Pheniram), clemastine (Tavist), clomipramine
(Clomicalm), acepromazine (Acevet, Atravet), fluoxetine (Reconcile) etc.

Important notes: You must not discontinue any medications without consulting your family
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.

6. Do not bathe the patient for 5 days prior to the appointment. following medications do not need to be discontinued: Essential fatty acid (evening primrose
oil, fish oil, Derm Caps, 3V Caps, EFA Caps, Actis Omega, Omegaderm, Welactin, Omega-Fend etc.), oral ciclosporin (Atopica), topical tacrolimus (Protopic), NSAIDS (Carprofen, Anafen, Ketoprofen, Metacam, Rimadyl, Deramaxx, Previcox), antibiotics (cephalexin etc.), antifungals (ketoconazole), oral pentoxifylline, immunotherapy (allergy shots), ear cleaners, flea medications, insect repellants, thyroid / heart / antiseizure medications, glucosamine, chondroitin sulfate, all other medications/supplements. 8. After meeting with the owner, a thorough examination of the patient and review of the medical history, we will present the various diagnostic and treatment options and their costs. 9. Be aware that intradermal test requires that the patient stay with us for several hours (typically 2-3 hours for dogs and cats and 4-5 hours for horses). We cannot guarantee that the intradermal test
will necessarily be performed on the day of the first appointment but it is usually possible.

10. If you have any questions about these guidelines, please do not hesitate to call the dermatology service
at: 519-824-4120 ext. 54615 or email us at: [email protected].

Source: http://www.ovc.uoguelph.ca/hsc/en/resources/451250Mar2013AllergyTestingInstructions.pdf