Allergies

Allergies can be fairly common in cats, just as in people, and can manifest in a variety of symptoms.  There are several things we can do to diagnose allergies and treat them.

Symptoms:

Allergy symptoms can be quite variable in cats depending on the type of allergy and the body system affected.  Some of the symptoms we can see are:

• Over grooming.  You may not see your cat grooming excessively, but you may see areas of thinned or no hair where they have licked it off.  This is their way of scratching itchy skin.  The most common areas seen are on the belly, the hindquarters, and the legs, but they can do it anywhere on the body.  Your cat may even groom so much that the skin becomes red, raw, and scabby.
• Miliary dermatitis.  This is when you notice multiple little bumps or scabs in various areas on your cat's skin.  The most common areas are on the back rear and around the neck, but again, these can show up anywhere.  This is like the equivalent of an allergic rash on your cat.
• Rubbing excessively.  Similar to over grooming, this primarily affects the skin above the eyes and on the ears.  You may notice that the fur above your cat's eyes is getting thinner and thinner, and that there are reddish scabs in the same area that are increasing in number. You may also notice that the hair on the ears is thinning out.  This is from overaggressive rubbing of the face on objects due to itchy skin that they cannot get with their tongue.
• Excessive ear wax production.  Many cats with allergies, even mild allergies, will have an increase in ear wax production from the systemic inflammation.  There are other causes as well for increased ear wax production such as yeast or bacterial infections, but allergies are the most common reason.
• Vomiting.  This happens most commonly with food allergies, if there is enough of an inflammatory reaction from environmental allergies, these can also cause increased vomiting.  The small intestine is a huge part of the immune system with lots of immune cells, so if the immune system is significantly inflamed from allergies, then the small intestine can also become inflamed, resulting in vomiting.
• Cracked paw pads.  While not as common, allergies in some cats can cause a dry crackled appearance to your cat's paw pads.
• Eosinophilic granuloma complex.  This is a hypersensitivity reaction generally caused by allergies that can cause swollen ulcerated areas of the lips, or red intensely itchy large plaque like scabby areas on your cat's skin.
• Scooting.  In rare cases, allergies can cause a thickening and itchiness of your cat's anal sacs resulting in scooting on the carpet to try and itch the rear end.  This can also be caused by impacted anal sacs, so if your cat is doing this, please let us know so we can check for impaction.
• Coughing.  While most commonly caused by asthma, coughing can also be triggered by allergies.

Diagnosis:

There are a few diagnostic tests that we can do to diagnose allergies, either definitively or presumptively.  These are:

• Allergy testing.  This is the ideal test for allergies, but even this is not 100%.  There are two types of allergy tests that can be done to diagnose allergies in your cat - a blood test looking for antigens and antibodies to allergens, or a skin test to determine which antigens your cat will react to.  Neither test is inexpensive.
  • The skin test will generally only be done by a veterinary dermatologist.  The skin test is considered more accurate, but also more time consuming and invasive.  If you are interested in doing the skin test, we can refer you to a board certified veterinary dermatologist who is a few hours away.
  • The blood test is done much more commonly since any veterinarian can draw blood and send it into a specialized lab.  There are multiple labs who perform this test, however not all labs are equal, and you may not always get accurate results.  We use Heska labs, considered one of the most accurate in the country by most immunologists.
• Diet trials.  Since many causes of allergies can be food allergies, we may want to try doing a hypo allergenic food allergy trial.  Since your cat cannot physically be allergic to something they have never eaten, a food trial consists of feeding your cat a commercial prescription hypoallergenic diet that does not contain any ingredients found in any over the counter diets.  For this to be effective as a trial, it must be fed exclusively for 4-6 weeks.
• Biopsies.  If your cat has skin lesions or is vomiting, and we are not sure if it is allergies are the cause, we can do full thickness biopsies of your cat's skin or small intestine to determine if allergies are the culprit.  This only tells us if allergies are the cause, it does not tell us what the specific allergens are, so we do not do this commonly.
• Response to treatment.  If your cat cannot do a hypoallergenic diet trial, then we may just try allergy treatment, and see if they respond.

Treatments:

Antihistamines.  These only work for some cats.  It is an inexpensive treatment that you can buy over the counter at the drugstore in pill form.  If you cannot pill, we do have some alternative routes of giving antihistamines.

• Zyrtec (cetirizine).  You can give your cat 1/2 of a 10mg tablet (5mg) once daily.  There are very few side effects to this.
• Chlorpheneramine.  This is an allergy pill that has been around so long that there isn't even a brand name for it anymore.  It is very inexpensive and will work for some cats.  The dose is 1/2 of a 4mg tablet (2mg) once or twice daily.  The primary side effects are drowsiness, although some cats can experience excitability.
• Benadryl (diphenhydramine).  This is effective in cats, but we do NOT recommend trying to give this to your cat orally.  Cats detest the taste of Benadryl. However, Benadryl is available in injectable form which you can use insulin syringes to administer, or we can have it compounded into a transdermal ear paste which has shown to be effective.
• Hydroxyzine.  This is actually a precursor to Zyrtec, which is metabolized in the liver to the active form of Zyrtec.  Because this was around much longer than Zyrtec, it is very inexpensive.  However, it must be given twice daily, or even three times daily in some cases.

Steroids.  Steroids are extremely effective in cats, but they have undesirable side effects.  The most common undesirable side effect of long term use is the development of diabetes.  We generally will try to minimize the length of time your cat has to be on steroids, or if your cat's allergies are year round, we will try to get to the lowest effective dosing to minimize the risk of diabetes.

Immunosuppressants.  The most commonly used immunosuppressant used in cats for allergies is cyclosporine.  This is an expensive drug whose side effects include anorexia and in rare cases, bone marrow suppression, but it can work very effectively, and is usually used when steroids are either not effective, or if your cat cannot tolerate steroids.

Immunotherapy.  This is done only when your cat has had an allergy test and we know exactly what environmental allergies your cat has.  These are allergy shots, customized for your cat to desensitize your cat to whatever they are allergic to.  We have had very good results with these, with very few side effects.

Removal of the allergens.  If your cat is allergic to something in their environment that you have some control over, if you can remove the source, then that will often fix the problem.  This would include things like fleas, laundry detergents, down comforters or pillows, etc.  If you cannot remove the source, but you can minimize your cat's exposure to it, that will also help.  Examples would be keeping the windows closed if your cat is allergic to outdoor pollens, using allergy filters in your ventilation and HEPA air filters to minimize dust mites, or feeding your cat canned food only or keeping their dry food in the freezer until feeding if your cat is allergic to storage mites.

If you have any questions or concerns on any of this, please feel free to contact us at All Feline Hospital at info@allfelinehospital.com.

This handout was written by Dr. Shelley Knudsen, DVM

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