Could Indoor Allergies Be Plaguing Your Cat?

Believe it or not, your pet's skin is a main thoroughfare for environmental allergens.

Watery eyes, itching, sneezing, coughing. Do indoor allergies cause you problems? Even if you dont suffer from indoor allergies, your cat may not be so fortunate. Though outdoor allergens (substances that can cause the immune system to respond with an allergic reaction), such as pollen, are considered to be the main


culprits in causing allergies, indoor allergens, such as the common house dust mite, actually have the potential to be much more reactive.

Is My Cat Suffering?

As humans, we generally have the most difficult time with indoor allergens when they are airborne and are inhaled into our upper respiratory tract. Though we consider our feline pets to be members of the family, most cats do not respond to airborne particles with an allergic reaction in the respiratory tract – unless the cat is asthmatic, notes William H. Miller, VMD, professor of medicine, chief of the section of dermatology, and medical director of Cornells Companion Animal Hospital.

Airborne indoor allergens can aggravate asthma in a cat that suffers from that chronic inflammatory respiratory disease. Signs of asthma vary from cat to cat but can include coughing and even wheezing – but since asthma is a disease of the lower respiratory tract (that is, of the lungs rather than the sinuses), even a cat with allergy-induced asthma (or allergies exacerbating the cats preexisting asthma) will not manifest the watery eyes and runny nose that are the hallmarks of human allergies.

In fact, the most frequent allergic response cats have to indoor, environmental allergens is not related to the cats respiratory system at all. “The most common route for environmental allergens probably is through the skin,” explains Dr. Miller, who is board-certified by the American College of Veterinary Dermatology. Skin contact with the allergens most often occurs when the cat steps on allergens that are piling up (microscopically) on floors and rugs, or lies down on allergen-packed beds and furniture.

An Immune System Response

When the cats skin makes contact with allergens (and if the cat is allergic to a particular substance), the felines immune system responds as if the skin were wounded – cells on the skins surface release inflammation-causing chemicals, such as histamine, which are important in the initial phases of wound healing. When there is no wound, however, the allergen-induced release of histamine creates an itchy sensation, which the cat will rub, scratch, claw and lick.

With a mild allergy, the cats change in behavior may be so subtle that the owner doesnt notice. If a cat has more severe allergies, however, its licking, scratching and rubbing can cause areas of hairlessness, irritated skin and open sores or wounds that can become infected. Allergies may also cause eosinophilic granulomas.


Eosinophilic granulomas can appear on the upper lip (indolent ulcers) as raised, reddish and moist growths (eosinophilic plaques) or as swollen or ulcerated lesions (eosinophilic granulomas with collagen degeneration). Of course, there are many possible causes for eosinophilic granulomas – with itchy, scratchy skin from allergies (that is repeatedly licked by a rough feline tongue) being just one. If allergies are the cause of the eosinophilic granulomas, determining what allergens are causing the itchy skin is important in order to heal the cats condition.

Common Indoor Allergens

In the home, the common house dust mite is frequently the main culprit in causing allergic reactions in cats, and is actually believed to be more allergenic than pollen, notes Dr. Miller. Other environmental particles that can trigger allergic reactions in the home include mold spores, disinfectants or deodorizers, cigarette or tobacco smoke, dusty kitty litter, carpet air-freshener sprinkles, cockroaches and their residues and, in some cases, even other pets. Birds can be a source of allergic discomfort to your kitty, says Dr. Miller, as well as bird “products,” such as down comforters and pillows.

Most indoor allergens circulate through the home in the air (which is where we come in contact with them), but eventually these particles come to rest on various surfaces. By keeping these surfaces clean and taking other specific precautions, you can effectively reduce your cats contact with some of the more problematic allergens.

For house dust mites, it is important to wash both your bedding and your cats bedding at least every two weeks in very hot water (130 degrees minimum). Vacuum floors, upholstered furniture and drapes regularly (all of which can harbor large numbers of a variety of allergens) and keep surfaces clean and free of food particles to discourage cockroach infestations. Dusty litter should be replaced with a more solid or pelleted litter. Keeping humidity inside the house below 50 percent and temperatures at 70 degrees or below year-round will discourage both the propagation of dust mites and the growth of mold.

Finally, experts recommend keeping heating, ventilation and air-conditioning systems properly maintained, repairing indoor water damage and considering replacing carpets with hard flooring and wallpaper with paint. As a general rule, dry, cool and clean conditions help keep levels of many allergens to a minimum. And if pollen is suspected to cause seasonal allergies, keep the windows closed!

Now What?

“A pet will benefit from any efforts the owner makes to provide a cleaner environment,” says Dr. Miller, but for many allergic pets, the effort is often not sufficient to relieve the pets constant suffering. Medicines such as antihistamines and corticosteroids can treat the signs of allergies and may be helpful solutions for some cases; however, immunotherapy may provide more lasting relief for a more severely allergic cat.

Immunotherapy involves injections of extremely dilute amounts of an allergen in order to desensitize the cat to a particular substance over time. In order for immunotherapy to be effective, the allergens must be pinpointed as closely as possible: “The success of the therapy depends on how well the vaccine describes the animals allergies,” says Dr. Miller. Determining a cats specific allergies usually begins with a basic allergy test that looks at a cats reactions to what are considered the 65 most problem-causing allergens; the test can be expanded to include hundreds of substances.

Once the major culprits are determined, the cats individual immunotherapy can begin – typically as a weekly therapy. As the therapy progresses, the allergen dilutions become increasingly concentrated, says Dr. Miller, with the therapys goal being to deliver a “full-strength” dosage of the offending allergen(s) to the cat with no allergic response – or a response so minimal that a “trivial” dose of antihistamine can render the cat completely comfortable. Though protocols vary, the practice at Cornells Companion Animal Hospital is to give maintenance injections once every three weeks once full-strength dosages are being administered with the desired results.

Immunotherapy is not, of course, effective with every cats allergies. Not all cats respond favorably to the therapy, and the source of some cats allergies can be quite elusive: There are literally millions of allergens that might cause a cat to react with itchy skin.

The good news is that there are several ways to help make an allergic pet more comfortable in the home – from environmental changes and prescription medications to immunotherapy programs – and that, for most allergic cats, one or more of these actions can give significant allergy relief. v