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Allergen Immunotherapy, Allergy Testing and Drug Withdrawal Times

By SASH Vets

Allergen Immunotherapy (desensitising or allergy vaccine) is often recommended by SASH Dermatologists for treatment of Atopic Dermatitis, as the only option that can reduce the need for life-long medications.

Atopic dermatitis is a complex inherited allergy, involving sensitivity to airborne allergens (pollens, mould spores, insect particles, dust mites, storage mites) together with skin barrier defects (“leaky” skin that allergens can penetrate, and is more prone to dryness and infections).

Avoidance of allergens is largely impossible: the allergens are very light and widely distributed in the air, irrespective of the plants in pet owners’ gardens and the thoroughness of household cleaning. Repair of the skin barrier is also not possible, but a skin care plan can help. Itch is very common, and it is important to reduce associated skin trauma (e.g. scratching, biting, licking) and improve patient comfort. Ultimately, we often need to use multiple concurrent treatments to achieve this, and the allergy vaccine helps to reduce the ongoing need for all medications.

The vaccine is made specifically for each patient based on allergy testing results; an intradermal (skin) test is most reliable, but we sometimes also use a specific blood allergy test (Allercept) to give more information. The protocol involves giving injections twice weekly for 8 weeks (the build-up phase of slowly increasing doses) then transitioning into a maintenance phase (typically a full dose of 1 mL every 3 weeks). These injections are often given by owners at home, although some prefer to have this done by their local veterinarian.

Allergen immunotherapy takes 6-12 months to help, with approximately 70-80% of dogs and cats improving, 60% with good to excellent response.  The vaccine may need to be continued for life to provide continued benefit, but some patients can be weaned off slowly after 2 years and maintain a good response.

Intradermal allergen testing involves placing an intravenous catheter and giving a light sedative (so pets lie very still while the tiny injections are given accurately), then clipping an area of fur on the side of the chest and injecting the allergens together with negative and positive controls (66 allergens; 74 injections in total).

It is important to withdraw some medications prior to testing:

Cortisone – short acting (prednisolone tablets, dexamethasone injections)6 weeks optimal (minimum 4 weeks)
Cortisone – long acting (e.g. Depo-medrol injections)12 weeks optimal
Cortisone – topical medications (e.g. eye, ear or skin drops/creams containing cortisone)1 week
Antihistamines (e.g. Zyrtec, Telfast, Polaramine, Iramine)1 week
Sedatives (some) e.g. ACP48 hours
Bathing48 hours
Antimicrobials (e.g. antibiotics, antifungals)Can be continued up to testing
Some allergy/itch treatments (e.g. Apoquel, Cyclosporin, Cytopoint injections)Can be continued up to testing

The Allergen Immunotherapy (Allergy Vaccine) Service is managed by the dermatology nurses. After the allergy testing, the dermatologist will organise a costing for the initial 6-months supply of vaccine based on the pet’s test results. A repeat supply will be required after 6-months. The allergens gradually lose strength over time. This occurs more slowly when refrigerated, so we advise that all allergy vaccines are kept refrigerated (although a few days out of the fridge at room temperature will have no to minimal effect).

Vaccines can be picked up directly from SASH (with the injection technique and protocol explained by one of the dermatology nurses) OR can be sent by courier or express post to the pet’s regular veterinarian. To minimise time out of the fridge, we only send vaccines to veterinary practices and do not send to private addresses where they are frequently held in post offices or collection depots awaiting owner collection.

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