Hyposensitization, more commonly known as allergy shots, is another dog allergy treatment option besides the use of corticosteroids and antihistamines.
Allergy shots for dogs usually require injections of diluted amounts of allergens (foreign proteins which trigger allergic reactions in the dog) on a weekly basis.
Skin Testing – Allergens or Just Antigens
Antigens are foreign proteins which may or may not trigger an allergic reaction (depending on the individual dog).
Allergens are antigens that cause an allergic reaction and the production of IgE in the dog’s body.
To determine which antigens are allergens for a particular dog, an intradermal skin testing has to be done.
The skin testing should be done during a time when the dog is not affected by allergies (e.g. in the winter if the dog is affected by pollen). If done during this time, the test will be more accurate because the skin responses will not be influenced by any active inflammation caused by the actual allergy.
Also, before the skin testing, the dog must be free from all corticosteroids, oral or injected, and antihistamines for a specified period of time in order for the test to be valid.
In order to test, a small amount of different allergen extracts (in all about 60 different substances are tested for) are injected into the skin and skin reactions are examined to see which allergen extract(s) triggered allergic reactions in the dog’s skin.
The vet can then compound a solution for the allergy shots. The solution contains the foreign protein(s) that have been found in the skin test to have caused allergic reactions to the dog.
The idea is that the dog’s body will be sensitized to the protein(s) and experience fewer allergic symptoms upon the next exposure to the allergen(s).
Working Mechanism of Allergy Shots
Veterinarians are unsure exactly how allergy shots for dogs work. However, there are several theories.
One theory is that allergy shots may cause a reduction in IgE levels (IgE antibodies bind to the allergens and mast cells causing allergy symptoms).
Another theory is that, like vaccination, immunization may be the mechanism in which a different class of antibodies is formed instead of IgE.
Yet another theory is that by giving allergy shots to a dog, the dog’s immune system will eventually develop a higher threshold of tolerance toward the allergens as the body forms allergen-specific suppressor cells that suppress the allergic response.
Pros and Cons of Allergy Shots for Dogs
If you are considering allergy shots for your dog’s allergy, you may be disappointed to find out that allergy shots are actually not commonly used in dogs because the cons far outweigh the pros.
Some difficulties when it comes to using allergy shots as a dog allergy treatment include:
Allergy shots take time to work – It takes at least 12 months to determine if a dog is responding to the allergy shots.
Relatively Low Efficacy
Not all dogs respond to allergy shots. In fact, only about 60 to 70% of dogs respond favorably to allergy shots, which means that about 30 to 40 percent of the dogs (especially those who are allergic to multiple allergens) being treated are still suffering from allergy symptoms at the end of the trial year.
Also, up to 25% of dogs will require prednisone therapy at some point during the course of treatment.
Potential Side Effects
Although side effects of allergy shots are not as serious and numerous as those of corticosteroids, allergy shots do have some side effects – one of which is the possibility of developing allergic reactions to the injected antigens.
Allergy shots are rather expensive. It costs over $100 for the sedation and intradermal testing, and over $150 for 12 injections.
Because of the above difficulties, many veterinarians use allergy shots as a last resort.