Have questions about allergy diagnosis and management? This FAQ section includes some of the most frequently asked questions about allergy in dogs and cats as well as diagnostic tips and immunotherapy. This information will help you provide the best care for your allergic patients.
General Dermatology
There are so many different words used to describe dermatology lesions; what are the specific differences between a comedo, papule, vesicle and a bulla?
It’s imperative to describe patient lesions accurately and correctly; this involves using proper dermatology vocabulary. There are subtle differences between some nouns used for lesions; the following definitions should help clarify the situation:
- Comedo (pl. comedones) – a dilated hair follicle filled with cornified cells and sebaceous material
- Papule – a solid, erythematous, circumscribed elevation of the skin up to 1 cm in diameter, causes include: inflammatory cell infiltration of the dermis, intraepidermal edema or epidermal hypertrophy
- Vesicle – a circumscribed elevation of the epidermis filled with serum; rarely seen in dogs and cats due to their skin fragility
- Bulla – a large vesicle, greater than 1 cm in diameter
What is the pathogenesis of pruritus in my patients with atopy?
Animals are exposed to potential allergens by inhalation and/or percutaneous absorption; susceptible individuals then produce excessive amounts of allergen-specific IgE antibody (or non-specific IgG). The IgE binds to the receptor sites of cutaneous mast cells; subsequent exposure will cause mast cell degranulation, a type-1 hypersensitivity reaction. Mast cell degranulation and activation results in inflammation which irritates the nerve endings of the superficial dermis; this initiates the sensation of pruritus.
There are many factors that contribute directly or indirectly to the pruritus experienced by atopic patients, these include: environmental temperature, high pollen and mold spore levels, genetic disposition, and concurrent pruritic dermatoses like flea allergy dermatitis, mite infestation, dermatophytosis, Malassezia dermatitis, pyoderma and food hypersensitivity.
In addition to the clinical signs what can help narrow down the list of offending allergens affecting my patients?
A thorough history is crucial when you are trying to identify allergens that cause your patients discomfort. Veterinarians often forget the importance of the season and geographical zone of the patient. To learn more about the significance of these and other important historical questions contact the Heska Medical and Technical Consultation Group at 1-800-GO HESKA, option 5.
Heska's Allergen-Specific IgE Testing and Sample Collection
How well do serum allergy tests compare with intradermal skin testing (IDST)?
Accurate measurement of allergen-specific IgE is crucial; the efficacy of allergen-specific immunotherapy depends on the accurate identification of offending allergens.
Accuracy of the ALLERCEPT® IgE test was validated in controlled studies of allergic dogs; the study is summarized below:
- Subject animals (dogs) were bred for high IgE responses then immunized with a single allergen; purified flea saliva, mites, grasses, or weeds.
- The animals were then skin tested by a board-certified dermatologist AND serum tested for allergen-specific IgE by commercial labs.
- The commercial labs did not know the dogs’ sensitization status.
- Test results showed that ALLERCEPT® IgE testing and conventional skin testing both correlated with the known sensitization of the dogs sensitized to fleas and mites.
- Commercial monoclonal and polyclonal antibody-based IgE tests reported numerous false positives and in the case of sensitivity to fleas they failed to detect that IgE to flea allergens was even present.
- Relying on test results with false positives would have resulted in the addition of unnecessary allergens in the treatment sets, thus reducing the overall effectiveness of treatment.
For additional details on the study call Heska’s Medical and Technical Consultation Group at 1-800-GO HESKA, option 5.
What are the recommended times of drug withdrawal for allergic patients if I want to use a serum allergy test?
If you are submitting a sample for Heska ALLERCEPT® serum IgE testing we do not require corticosteroid withdrawal for patients on medication for less than three months. For patients who have been on steroids for more than three months we recommend the following minimum withdrawal times in order to optimize the detection of allergen-specific serum IgE using ALLERCEPT®:
Oral
- Prednisone, Prednisolone, Temaril-P 45 days (if >0.25 mg/kg)
- Methylprednisolone 45 days
- Triamcinolone (Vetalog) 60 days
Injectable
- Triamcinolone (Vetalog) 60 days
- Methylprednisolone acetate (Depo-Medrol) 90 days
Topical
- Otic and Ophthalmic Preparations 30 days
- Steroid shampoos 30 days
- Sprays 30 days
Other
- Antihistamines No withdrawal necessary
For further assistance, call Heska’s Medical and Technical Consultation Group at 1-800-GO HESKA, option 5.
Another company claims to have the same serum allergy test technology as Heska; is this true?
Heska is the world leader in innovative solutions for veterinary allergic disease. Heska holds over 250 U.S. and International patents covering its unique allergy technology. Many human pharmaceutical companies have agreements with Heska for development and use of receptor technology in their human allergy products. Other companies try to copy Heska’s technology but no one possesses the superior and proprietary detection reagent for measuring allergen-specific IgE in the serum of both animals and humans.
The unique, patented ALLERCEPT® program can detect as little as 70-140 picograms (trillionths of a gram) of allergen-specific IgE and can be used alone or in conjunction with conventional IDST to accurately identify the source of an animals’ allergy.
Many other serum IgE tests produce false positive results; they mis-identify the patient’s allergen sensitization because they detect allergen-specific IgG in addition to IgE. This causes the test to be non-specific; it should be measuring IgE, not IgG. Since IgG will not bind to the high affinity IgE receptor, Heska technology helps to assure that such false positives do not occur.
When is the best time to submit a serum sample on my atopic dermatitis patients?
The best time to collect a sample is when the patient is clinical; they need to be affected long enough that they have diagnostic levels of IgE but the clinical signs are not so severe they are miserable.
Ideally a sample should be collected prior to administration of any steroids.
Late summer or fall are appropriate times to collect a sample if pollens are a concern.
Is it safe to store a patient serum sample if we can’t submit it for allergy testing immediately?
A properly separated serum sample can be safely stored for up to 6 months after collection if kept in a ”deep freeze”. Deep freeze refers to a sample placed in a freezer without a periodic defrosting cycle. These freezers are usually separate, horizontal “chest” freezers, not freezers associated with a refrigerator. If you have other questions about integrity of patient samples please call Heska’s Medical and Technical Consultation Group at 1-800-GO HESKA, option 5 for expert advice.
Environmental Recommendations
What can I recommend to minimize my patients’ exposure to storage mites?
Storage mites are very common and are strongly allergenic. They develop where there is moisture or high humidity, often in association with mold. They may be found in house dust, and in stored products such as flour, grain, cheese, seeds, straw, cereal foods, and pet foods. The following recommendations will help control storage mites:
- Freeze food in small portions or store pet food in air tight containers; do not feed old or outdated pet food.
- Wash containers frequently in detergent and hot water (130°F); dry completely before refilling with food.
- Appropriately dispose of empty pet food bags
- When purchasing food check bag for holes and tears; do not stockpile food, purchase only what is needed.
- Feed a canned diet
What can I recommend to minimize my patients’ exposure to molds?
Fungi are saprophytic and parasitic plants found both indoors and outdoors in moist organic materials.
For outdoor spore levels, decrease exposure to leaf litter, peat moss, mulches, soil and rotting logs.
Careful attention to general cleanliness, reducing indoor moisture and remediation of known mold sources is necessary to control indoor mold levels.
What can I recommend to minimize my patients’ exposure to pollen?
The ubiquitous nature of pollen makes avoidance impractical but exposure can be minimized. The following are suggestions for your patients and their environment:
- Outdoors – Lessen exposure to certain conditions and times of day; if possible, avoid, windy days, high humidity and early morning or evening hours. To check the pollen levels in your area go to www.pollen.com.
- Indoors – Vacuum and dust frequently; use air conditioning instead of opening the windows
- Patient – Keep off the lawn for several hours after mowing; use a damp cloth to wipe feet, body, and face after being outside; keep pet groomed and clipped to decrease pollen collection; discourage pet from sticking head out the window when traveling in the car; bathe frequently with hypoallergenic shampoos, leave-in conditioners and cool water rinses; dry bedding in the dryer instead of hanging outside.
What can I recommend to minimize my patients’ exposure to dust mites?
Dust mites (Genus Dermatophagoides) are common in the environment and feed on dander (human and animal), skin scales, and hair. They thrive in humidity of 50% to 70% and are commonly found in beds, mattresses, carpets, sofas, and pet bedding. Total elimination is impossible; control measures are aimed at inhibiting mite multiplication thereby reducing the effect on the patient. At a minimum, pet sleeping areas should be maintained according to the following guidelines:
- Avoid carpeting; hardwood, vinyl, and tile are better
- Remove ‘dust collectors’, i.e., books, stuffed animals, newspaper piles
- Wash pet bedding weekly in hot water (130°F)
- Change furnace and air conditioning filters frequently; use filters specifically made for allergen control
- Avoid feather and wool bedding, use allergen-proof bed covers and encase box springs in vinyl or plastic covers
- Vacuum and dust frequently preferably when pet is outdoors and use a vacuum with a high-efficiency particulate air (HEPA) filter or a double-layered micro filter bag
- Groom pets frequently
Results and Immunotherapy
How reliable are the results from serum allergy testing with respect to food?
Heska, in agreement with the American College of Veterinary Dermatology, does not recommend IgE testing for foods. An exclusionary diet trial, followed by provocative re-challenge, is recommended for animals suspected of suffering from adverse reaction to foods.
My patient is allergic to 23 substances but their immunotherapy sent only contains 12 components, why?
The best results are obtained when immunotherapy sets consist of the minimum number of relevant allergens. This approach assures that the requisite concentrations of the major allergens necessary to effect the immunological changes are given. The immunotherapy recommendations provided by Heska are based on the following parameters:
1. The botanical zone based on city and zip code of the clinic.
2. The seasonality of the allergic disease, as described in the patient history.
3. The number, distribution and strength of reactivity to allergens.
4. Knowledge of allergen cross-reactivity, and intensity of pollination.
5. Pollens of allergenic importance.
Why aren’t mold extracts included in immunotherapy prescriptions?
Mold extracts are not typically included because they are very crude and contain proteolytic enzymes that can affect the potency of other allergens in the mixture. As a result their inclusion is usually not advised. If mold extracts are desired in the immunotherapy prescription, we recommend ordering them separately for injection on their own or adding a second vial containing molds later if the patients’ response to the initial therapy is suboptimal. Remember, as the prescribing veterinarian the ultimate choice is yours.
What is the success rate for patients on immunotherapy?
While every pet responds differently to any given medication, immunotherapy has been found to be successful in 60-70% of patients. Of these patients the degree of improvement will vary but is not typically 100%.
Immunotherapy is the only therapy that targets the root cause of allergic reactions; other treatments just mask the symptoms. It is important to remember your patients’ allergies won’t be ‘cured’ but they can be safely and effectively managed
How long until we will see results in our immunotherapy patients?
Each patient will respond differently to immunotherapy but most treated animals respond positively showing relief in 4-12 months. It is recommended that immunotherapy be continued for at least twelve months before deciding whether or not it is the best way to manage your patient’s allergies.
Once a maintenance dose of immunotherapy has been attained and a proper injection schedule established patients may be safely maintained on immunotherapy for their lifetime.
How can a patient with an appropriate history and clinical signs for atopy test negative (for everything) on a serum allergy test?
There is a subset of patients whose history and clinical signs are consistent with a diagnosis of atopic dermatitis but their serum IgE test results do not support the diagnosis. There are many variables that can produce this type of result; for these challenging cases, call Heska’s Medical and Technical Consultation Group at 1-800-GO HESKA, option 5 for expert advice.
Why is it recommended to give the first injection from a refill vial of immunotherapy at half the maintenance dose?
Over time the potency of the allergens in a treatment set decreases; when you receive a new vial it is at full potency. To allow your patient to adjust to the new vial, we recommend administering half of the maintenance volume for the first injection (from the refill vial). If reactions are NOT reported administration of the full maintenance volume may be resumed with the next scheduled injection.