Most people know someone who gets periodic “allergy shots” for airborne allergies. What this means is that a special individually-made serum is created using small amounts of allergens (proteins against which the person reacts). Usually some kind of scratch test in the skin is used to determine what the best ingredients for the serum will be. It may seem odd that injecting someone with proteins we think they are allergic to would be helpful but it is. And we still, after all these years, do not know why it works. But it works for dogs and cats, too.

What to expect from immunotherapy

Approximately half the dogs receiving immunotherapy will have an excellent response. About 25% will have a so-so response. About 25% will not have any response at all.

It can easily take a year to determine if the pet is responding.

Many people go marching off to the veterinary dermatologist with their itchy pet with the idea that immunotherapy will have an immediate effect and nothing could be further from the truth. Immunotherapy takes weeks to months to work and is something one plans for “next season” rather than for problems going on this allergy season.

Immunotherapy is not going to help a patient with a food allergy.
A patient with a food allergy needs a food trial, not allergy shots

When immunotherapy is combined with other forms of itch relief, even better results are obtained.

It starts with an “allergy test”

The term “allergy test” is probably not the most accurate for the type of testing that is used to select serum components. The substances that create strong reactions are not necessarily what the patient is “allergic” to. Still, selecting allergens for serum starts with either a skin test, a blood test or both.

With the skin test a patch of fur is shaved and a grid of allergens are injected into the skin to see which elicit the most redness and swelling.

With the blood test, it is Immunoglobulin E (the antibody of allergy) levels directed against specific antigens which are measured.

From this information, the most reactive allergens are identified but it is also the patient’s exposure level to these allergens which determine whether or not they go into the serum. Pollens, fabrics, molds, and insect parts are commonly tested. A special company that manufactures allergy serum is contracted to make an individual patient’s serum.

Administering Injections

Allergen doses are reflected in units called PNU (protein nitrogen units). The initial vials of serum are the weakest (maybe 1,000-2,000 PNU per ml). The patient will receive an increasing amount of allergen over time and will finally end with a maintenance vial that might be as concentrated as 20,000 PNU per ml.)

There are many dosing protocols that may be selected. Ideally the owner will be giving the injections at home but if this is not possible, the pet can be brought to the hospital for allergy shots. You will receive a schedule showing when to give each injection and how much to give. The amounts will increase until it is time to move up to the next vial where the concentration of allergens in greater.

Expect to be thoroughly educated in the art of giving injections at the time the serum is prescribed. It may seem daunting at first but is very simple. It is helpful if the pet receives a special reward after injections. Used needles can be disposed of in the regular trash but it is helpful if they are placed inside a plastic or metal container (like a liquid laundry detergent bottle or closed coffee can) so as not to cause an accidental puncture.

Injections should be timed in such a way that the pet can be observed for 30-60 minutes post injection so as to watch for reactions. Any reactions should be reported to the veterinarian before giving the next injection. Serious reactions are rare (less than 1% of patients have them) but you should still be able to recognize them.

Serious Reactions Requiring Immediate Intervention

• Hives
   
• Facial Swelling
   
• Vomiting or Diarrhea
   
• Collapse

Not So Serious Reactions Which Still Require Reporting

• Itching
   
• Listlessness
   
• Swelling at the injection site
   
• Excess panting
   
• Frequent swallowing
   
• Loud Stomach/Intestinal Gurgling

Reactions are likely to lead to some kind of adjustment of the protocol. Be sure you understand when you are supposed to return for any rechecks.