Treatment of Allergies
How to Deal with the Food Allergy Suspect: The Hypoallergenic Diet Trial
The Basic Principle
To determine whether or not a food allergy or intolerance is causing the skin problem, a hypoallergenic diet is fed for a set period of time. If the pet recovers, the original diet is fed for up to two weeks to see if itching resumes. If recovery is seen with the test diet and itch returns with the original diet, then food allergy is diagnosed and the pet is returned to either the test diet or another appropriate commercial food indefinitely.
What is a Good Hypoallergenic Diet?
There are two approaches to this question. Obviously, the test diet must be of a food source that the patient could not possibly be allergic to. The traditional method is the use of a novel (new to the pet)Â protein and carbohydrate source; that is, something the pet has never eaten before. In the past, lamb has been the protein source of choice as American pet food companies had traditionally failed to produce lamb-based pet foods. Unfortunately, recent production of lamb and rice-based foods has removed lamb from the acceptable hypoallergenic diet list for most pets.
Fortunately, many pet food companies have discerned the need for diets using unusual protein and carbohydrate sources with a minimum of additives. Foods can be obtained based on venison and potato, fish and potato, egg and rice, duck and pea, and even kangaroo. Diets used for allergy trials must contain basically one protein and one carbohydrate source and neither can be something the pet has had before. Recently several diets that include duck, venison, and so on have been released to the general market. Be aware of foods that contain these ingredients because these ingredients will not be useable for future diet trials if they were ever used in the pet’s regular food.  Consult your veterinarian for guidance in choosing a diet.  It may also be helpful to bring the label from your current food to your appointment.
It is important that no unnecessary medications be given during the diet trial. No edible chew toys (such as rawhides or bones) should be given. Treats must be based on the same food sources as the test diet. (Beware of rice cakes, though, as wheat is commonly used as a filler.) Chewable heartworm preventives should be replaced with tablets. Â Again, your veterinarian should be consulted to help with these choices.
Home cooking was originally the only option felt to be appropriately free of allergens but for most animals these special commercial foods are adequate. Occasionally home cooking ends up being necessary after all. Recipes for appropriate diets can be purchased through www.balanceit.com, a website set up by the American College of Veterinary Nutrition.
The Hydrolyzed Protein Method
Recently a new approach has been introduced using therapeutic diets made from hydrolyzed proteins. This means that a conventional protein source is used but the protein is broken down into molecules too small to excite the immune system. Some hydrolized diets are on the market; discuss with your veterinarian which is best for your pet.
How Long to Feed the Trial Diet
In the past, four weeks was thought to represent a complete trial period. More recent work has shown that only one food allergic dog in four will respond within this time frame and that a more appropriate trial period would be 10 to 12 weeks. This may be an extremely inconvenient period of time to home cook. Some veterinarians recommend a recheck appointment or a phone call after four weeks of diet trial and then again after 8 weeks. Eighty percent of food-allergic dogs will have responded to diet trial at least partially by six weeks.
Most commercial diets used in food allergy trials have a 100% guarantee. This means that if your pet doesn’t like the food, the food can be returned for a complete refund, even if the bag is opened. This is especially helpful for feline patients, as cats are famous for being choosy about what they are willing to eat.
 What to do if the Diet is Successful?
To confirm food allergy, return to the original food; itching resumes within 14 days generally if food allergy was truly the reason for the itchy skin. Many people do not want to take a chance of returning to itching if the patient is doing well; it is not unreasonable to simply stay with the test diet if the pet remains free of symptoms. Often it is difficult to remember 10 to 12 weeks later how itchy the dog used to be before the diet trial. The diet challenge helps make it more obvious whether the diet trial has worked or not.
It is possible to more specifically determine the identity of the offending foods after the pet is well. To do this, a pure protein source (such as cooked chicken, tofu, wheat flour or any other single food) is added to the test diet with each feeding. If the pet begins to itch within 2 weeks, then that protein source represents one of the pet’s allergens. Return to the test diet until the itching stops and try another pure protein source. If no itching results after two weeks of feeding a test protein, the pet is not allergic to this protein.
Treatment of Atopy (inhaled or skin allergens)
Treatment Options
Before doing anything else, it is important to clear up secondary infections. Secondary infections involve bacteria (usually Staphylococcal) and/or yeast (Malassezia) at the site of the itchiest areas. These organisms live naturally in the skin but when the skin is irritated, they gain access to inner tissue layers and proliferate. Sometimes they generate further allergic response. These infections tend to be recurrent and are the usual cause of recurrence of itch symptoms in a patient previously controlled.
Making the Skin Less Reactive
Since it is unlikely that the patient is going to be able to avoid airborne allergens (pollens, for example, travel miles in the breeze), we are left with treating the patient. For short episodes of itching during the itchy season, cortisone-type medications are highly effective. When the pet becomes more chronically itchy, cortisones become less feasible because of their long-term side effects and other options must be considered.
Steroid Hormones
These cortisone-type medications (prednisone, prednisolone, triamcinolone, dexamethasone etc.) tend to be useful as the first line of defense against itchy skin. A higher dose is used at first but this is quickly tapered down once the condition is controlled. Prednisone, for example, is given every other day so as to allow the pet one day of recovery from the prednisone’s hormonal actions. An atopic dog will respond within days. For cats, long-acting cortisone-type injections are commonly used as cats are frequently not amenable to taking pills.
Side effects include:
- Excess thirst
- Excess hunger
- Excess urination (which can lead to house-breaking issues)
Omega 3 Fatty Acid Supplements
These products are NOT analogous to adding oil to the pet’s food. Instead, these special fatty acids act as medications, disrupting the production of inflammatory chemicals within the skin. By using these supplements, it may be possible to postpone the need for steroids/cortisones or reduce the dose of steroid needed to control symptoms. It takes a good 6 weeks to build up enough omega 3 fatty acids in the body to see a difference.
Antihistamines
These have far fewer side effects than prednisone, but only 10-20% of dogs will respond to any given antihistamine. Fortunately, there are numerous antihistamines to try and often it is possible to find one that works by trying a different one sequentially. In contrast to dogs, cats are far more responsive to antihistamines; the downside is having to give a cat medication twice daily. Antihistamines and omega 3 fatty acids synergize with each other so it is a good idea to use omega 3 fatty acids in conjunction with antihistamines.
Cyclosporine
Cyclosporine is a modulator of the immune response that has been very helpful in organ transplant patients both human and non-human. It has been found to be as reliably effective in atopic dermatitis in the dog as steroids and does not carry the unpleasant side effect profile that steroids do. It is used mostly in dogs but can also be used in cats. This medication may be recommended by your veterinarian if steroids and antibiotics are not effective.
Reducing Allergen Exposure
The following are some general tips for minimizing allergen exposure.
Bathing the pet weekly to remove allergens from the fur may be helpful in reducing allergen exposure. There are also many therapeutic shampoos that can be used to restore the skin’s natural barrier or to assist in general itch relief.Â
- Avoid stuffed toys and wash bedding regularly to minimizes dust mite exposure. Also, remove the pet from the area when vacuuming or dusting.Â
- Use air-conditioning and/or an air filter system.Â
- Keep the pet away from the lawn while it is being mowed.Â
- Minimize houseplants.
Immunotherapy for Allergies
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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 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 a skin test, a blood test, or both.
With the skin test, a patch of fur is shaved and a grid of allergens is injected into the skin to see which elicit the most redness and swelling.
With the blood test, what is measured are Immunoglobulin E (the antibody of allergy) levels directed against specific antigens.
From this information, the most reactive allergens are identified but it is also the patient’s exposure level to these allergens that determine whether or not they go into the serum. Pollens, fabrics, molds, and insect parts are commonly tested. A 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 it’s 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 to 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 that 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.
“Overgroomingâ€, “Barbering†or Fur Mowing – A Specific Feline Problem!
This symptom is in short that the cat is licking off all his or her hair. Often the belly is nearly as bald as if it were shaved. Sometimes a Mohawk of normal fur makes a stripe down the back, surrounded by bald spots on either sides. Sometimes it is the lower back itself that is bald.  Other common areas include the backs of the front or hind legs. In some cases this behavior can be psychological, but in many cases cats that barber lick off their hair because they itch. For example, in a recent study of 21 cats referred to the University of Guelph Veterinary Teaching Hospital Behavior Service because of excessive hair licking, only two cats were ultimately believed to have a psychological reason for hair licking, sixteen cats were found to have a true medical basis for itching, and three cats had both.
How Do we Know the Cat’s Hair is not Simply Falling Out?
Cats often do their licking when no one is watching, so you may not see your cat grooming excessively. One might wonder why it is that the itchy dog creates moist, red, oozy, unpleasant looking “hot spots†while the itchy cat cleanly licks away only the hair leaving the skin itself not in the least bit scabbed, red, or even raw. Leave it to the cleanly nature of the cat!!
There are a few rare diseases that actually will lead a cat to lose hair in great patches, but this is extremely unlikely.
Obvious Reasons to Itch
The first step is to rule out the obvious causes of itching (this is true for any allergies!!). Â The easiest such cause to rule out is a flea infestation. If live fleas or flea dirt are seen in the coat, then the answer is obvious. If fleas are not seen in the coat, one cannot assume there are no fleas to be found particularly if the lower back is one of the balding areas. Cats are very efficient groomers and can lick away all traces of fleas so we may need to go by the pattern of hair loss (lumbar, possibly including scabbing around the neck), seasonality of the hair loss, and response to flea control. The first step is always ensuring immaculate flea control.
Figuring out the Not-So-Obvious Causes
A step-by-step process is important in ruling out hidden allergies, parasites, and even ringworm.
First, the non-invasive tests are performed:
- Several skin scrapes (ideally, if feline Demodex mites are present, they will be found, though sometimes this is not the case. Notoedres or Cheyletiella mites generally produce more obvious skin damage).
- A fecal flotation test for parasites (occasionally intestinal worms will create itching in the skin. Also, Demodex mites sometimes show up in the fecal test rather than the skin scrape because the cat has been so efficient at licking them up.)
- Checking the ears with otoscope (even if the itchy areas are distant from the ears sometimes ear mite travel out of their normal homes in the ear canal).
- Inspection of the cat with a Wood’s light (a fluorescent light – hairs infected with ringworm fungus often glow in the dark) plus a culture for ringworm. The culture will require approximately 10 days to grow.
Skin Biopsy
This can likely be accomplished the same day as the initial visit and yield results as soon as 48 hours later. It is important that the samples be read by a pathologist who specializes in reading skin tissue so your veterinarian may need to request a special expert or use a special laboratory. In this procedure, a local anesthetic is injected into selected areas of skin and an instrument called a punch biopsy (which resembles a tiny cookie cutter) is used to remove small plugs of skin. The cat will probably have a stitch in each area where a sample was taken.
- The absence of abnormalities in the tissue virtually confirms a psychological (the more correct term is psychogenic) cause of the mowing. (In the Guelph study mentioned above, three cats had both psychogenic mowing AND medical disease).
- Ringworm can be confirmed more quickly than with the culture (the culture sometimes picks up ringworm when the biopsy does not, though, so doing both tests is very reasonable.)
- The presence of allergy should be readily identified (though it will not be possible to tell what type of allergy: insect-related, food or airbourne).
Food Allergy Trial
Food allergy commonly produces non-seasonal barbering in cats. This mowing may or may not be responsive to cortisone-type medications. The only way to determine if the cat has a food allergy is to put the cat on a trial diet that the cat could not possibly be allergic to (either a hydrolyzed protein veterinary diet or a novel protein veterinary diet) for a long period of time and see if the barbering stops. How long? Most cats respond in 3 to 4 weeks but some require 8 weeks, so a 2-month trial is typically recommended.
- The advantage of this test is that it makes the diagnosis, and it also provides treatment.
- There are two important disadvantages of this test. The first is that no results will be available for up to 2 months. The second is that many cats are picky about the diet food and it may be hard to find one the patient likes. If the cat goes outside, it will not be possible to do a food trial as it will not be possible to control what the cat eats.
Flea Control Trial
As mentioned immaculate flea control is very important in ruling out fleas as a cause of the mowing. To be sure about fleas, a reliable flea product such as Revolution or Frontline. If Frontline is used, it must be purchased from a veterinary office to be reliable and not counterfeit products or improperly stored. Â Frontline applications tend to wane in the last 10 days of their use allowing fleas to bite before they are killed by the product. For this reason, to maintain adequate skin levels of product for the trial, some experts recommend using the product more frequently than labeled by the manufacturer. Â Seek advice from your veterinarian before using these products more often than labeled.
- This trial only answers the question of whether or not the problem is flea-related and it takes approximately 2 months to do so.
- To properly determine if there are fleas in the household, a flea comb should be used, ideally on a pet that is not itchy or mowing. Flea combs have special narrow teeth that can trap live fleas and flea dirt.
Steroid Trial
For this trial, the patient receives some kind of cortisone-type treatment for 3 to 4 weeks. At the end of that time one can tell if the barbering has improved (and the barbering is said to be “steroid responsiveâ€) or the barbering has not improved at all. Knowing whether or not the barbering is steroid responsive helps classify possible causes. For example, seasonal steroid responsive barbering is most likely to be from fleas (technically allergy to the flea bite) or an airborne allergy. Non-seasonal steroid responsive barbering is often from a food allergy.  Many experts like to do the steroid trial at the beginning of the work up while others wait until more results are in.  A steroid trial is very inexpensive and one of the least labor intensive tests that can be done.
What if the Cat Really has Psychogenic Overgrooming?
Psychogenic overgrooming is an obsessive disorder of unknown causes. Â These cats have nothing physically wrong with the skin, and no discernible allergies, but continue to barber. Â The approach to these kitties is often aimed at environmental enrichment. (See blog entry on Feline Environmental Enrichment) Â This can include offering more toys, more games (feeding in a different location daily to create a hide-and-seek sort of cat entertainment), and more attention.Â
In addition, medications can be used to help the cat become less obsessive. Â Clomipramine, Amitriptylline and Fluoxitine are all medications that your veterinarian may suggest for treatment.
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