Fatal reactions have been rarely and anecdotally described. I have practiced more than 25 years as a dermatologist in a referral
setting, seeing 100% dermatology cases only. In addition, I work with 13 other dermatology specialists at three full-time
and six part-time veterinary dermatology practices, and together we have treated thousands of dogs with immunotherapy. In
all these clinics, only one dog has had a fatal reaction. I am also a consultant for a commercial laboratory that serves veterinarians
in four states and have not learned of other reports of immunotherapy that resulted in anaphylaxis and death.
Figure 7. The V-shaped skin fold in a shorthaired dog.
Reactions that require immediate veterinary attention can occur with any injection, though more severe reactions usually occur
in the first few months of therapy and can occur as early as the first injection.
Figure 8. Insert the needle into the center of the V-shaped skin fold parallel or at up to a 30-degree angle from the plane
of the back or neck.
Treatment for urticaria is usually limited to hydroxyzine (2.2 mg/kg orally b.i.d. for one or two days). If this is not effective,
then prednisone (1 mg/kg orally) is usually effective; if the immunotherapy injections caused the urticaria, then one or two
days of prednisone therapy is all that is required.
Angioedema is treated with oral or injectable methylprednisolone (1 mg/kg) and diphenhydramine hydrochloride (2.2 mg/kg) given
Anaphylaxis is the most serious complication, and dogs should be treated as soon as possible with intravenous methylprednisolone
(1 mg/kg) and diphenhydramine hydrochloride (1 mg/kg not to exceed 40 mg). If a dog presents in severe shock (i.e. has collapsed and has hypotension), then intravenous epinephrine (0.01 mg/kg) should also be given. Some dogs will improve
within 15 to 30 minutes even without treatment and may have already recovered while the clients were bringing the dog to the
clinic for care. In these cases, treatment may not be required or antihistamines may be given orally.
Figure 9. Owners should hold the syringe like a dart and touch the plunger only after inserting the needle subcutaneously.
Evidence of milder allergic reactions that should be reported to the veterinarian before a client gives any more injections
are increased itching, listlessness, sleepiness, and anxiousness. Pain or swelling at the injection site is infrequent and
minimal if injections are given correctly and animals are trained to accept the injections. If an owner is varying the injection
location as instructed, these reactions may be due to inadvertent intradermal injection. Other reactions that may be seen
are panting, hyperactivity, increased bowel sounds, changes in urinary habits, and frequent swallowing.
Most reactions occur relatively rapidly after the injections, but changes in activity and pruritus may occur one or two days
later. Patterns of pruritus in relation to when injections are given should be monitored, as this is often the basis for making
adjustments in the treatment protocol. It is helpful to have clients grade pruritus and note its location. Clients should
grade their dogs' pruritus from 0 (no pruritus) to 10 (most severe pruritus for this dog before hyposensitization) before
starting the therapy and as frequently as they can during the first few months of therapy. Encourage clients to keep a diary
of their observations, which may be helpful in determining allergen adjustments.
ADJUSTING THE PROTOCOL
Immunotherapy protocol adjustments are often needed within the first two to four months, so rechecks should be scheduled.
Some dogs require adjustments within the first month, and this can be determined only if the dogs are not receiving glucocorticoids
during the induction phase. If a pet reacts during the induction phase, go back to the last dose that produced no reaction,
repeat it twice, and then see if you can gradually increase the dose to the amount indicated in the protocol. If the pet still
reacts, then the last dose it did not react to is that pet's maximum injection volume and concentration.