ADVANTAGES AND DISADVANTAGES
One big advantage of SLIT is the ease of administration. Although many owners do not mind giving injections to their pets,
most do not relish it and are happy to be presented with an alternative. Most dogs accept SLIT administration easily, even
viewing it as a treat, which increases compliance. However, successful SLIT requires faithful daily administration, and owners
with busy schedules may find it more convenient to give a less frequent injection.
Data from a supplier (including several thousand dogs) indicate that adverse reactions to allergy drops may occur in about
4% of dogs.9 Nearly all of these reactions are mild and temporary and almost never require cessation of treatment. Most occur soon after
starting treatment but disappear within a few days or a week of continued treatment.
The most common reaction is transient worsening of clinical signs, usually increased pruritus. A few dogs may rub or scratch
at their mouth after administration, perhaps analogous to the oral itch that some human SLIT patients experience. Occasional
stomach upset or vomiting has been observed in a few dogs.
In people, anaphylactic reactions to SLIT are rare to nonexistent, and SLIT can be given to people with a history of reaction
to allergy injections. In the experience at the University of Wisconsin's School of Veterinary Medicine, the same is true
in dogs. We have safely treated numerous patients with SLIT that have had anaphylactic reactions to allergy injections.
PROTOCOLS FOR SLIT IN DOGS
Initial diagnostic and allergen testing
In general, do what you have always done. The process of diagnosing atopic dermatitis through diagnostic testing to eliminate
other possibilities and follow-up allergy testing are the same whether you plan to treat with SLIT or allergy injections.
Any combination of serologic or intradermal testing techniques may be used to establish the individual sensitivities of each
Allergen selection and formulation
After careful testing, the principles for choosing the allergens in the prescription are exactly the same as those used when
choosing allergens for injection ASIT mixtures. SLIT formulation suppliers (Table 1) are familiar with these principles and will provide a suggested formulation based on the allergy test results for each patient.
Table 1: Sublingual immunotherapy veterinary formulation suppliers
Treatment involves a series of three bottles of escalating concentration. The allergen solution should remain in contact with
the oral mucosa for as long as possible. People are instructed to hold the solution under their tongue for one minute before
swallowing. Obviously, we cannot request the same of dogs, but it is important that the solution is dispensed directly into
the oral cavity, not in food, and that the dogs refrain from eating or drinking for five to 10 minutes after the dose is given.
Multiple daily administrations are required for efficacy in people, and our clinical group strongly recommends that owners
be counseled to administer the allergy drops twice daily, every day. If they forget to give a dose in the morning, they should
give one in the afternoon and one before bed. This twice-daily dosing schedule is indefinite for the duration of therapy with
no tapering. It should be mentioned that each SLIT formulation supplier has established its own protocol for allergen concentrations,
dosing volumes, frequencies, and schedules; comparative studies of different protocols have not been performed.
It is easy to switch a patient from injections to drops. Three possible situations exist.
1. If the patient has had no response to allergy injections, I recommend the standard protocol, starting SLIT with the lowest-concentration
bottle and escalating.
2. If the patient is stable and has been doing well with the injections (perhaps the owner is just tired of giving them),
you can typically start directly with the maintenance vial of SLIT, with no need for the escalation phase.
3. If the patient is being switched to drops because of an adverse reaction to allergy injections, I recommend cautious administration
of the lowest-concentration vial at first. If there seems to be any adverse reaction or worsening, reduce the concentration
At this time, the ideal total duration of treatment is not known in dogs. In people, daily administration is continued for
two to five years. After this time, if the patient is stable, treatment can be discontinued, and the effect appears to be
permanent in nearly all cases. Whether that is true in dogs is unknown.
As with injection ASIT, it is important to re-evaluate patients receiving SLIT on a regular basis (e.g. after three, six, and 12 months of treatment, which is what we use in our clinical group). My subjective clinical impression
is that response to SLIT often occurs quite rapidly—some dogs are improved three months after starting SLIT treatment, and
most that will respond show at least some improvement, if not substantial improvement, after six months of treatment.
If any adverse reactions occur or persist, it may require lowering the allergen dose. You should contact the SLIT supplier
for specific instructions as to how to accomplish this for that specific formulation.
There is much still to learn about this new allergy treatment. Even in human medicine, which has been using SLIT for more
than 40 years, there is still debate about the optimal dosing schedule. I look forward to further studies in dogs that will
provide additional evidence of efficacy based on controlled trials, will compare dosing regimens, and perhaps will compare
this therapy more directly to ASIT administered by injection.
Editors' note: Dr. DeBoer is a consultant to Heska, manufacturer of Allercept Therapy Drops, but has no financial interest
in any sublingual immunotherapy product.
Douglas J. DeBoer, DVM, DACVD Department of Medical Sciences School of Veterinary Medicine University of Wisconsin Madison,