Every other week, Dr. Patrick Tate, chief of the veterinary staff and a general practitioner at Webster Groves Animal Hospital, answers reader questions about pets. This week's question comes from Rebecca Daniels.

Question: What causes people to be allergic to cats, and is it more of a problem than with dogs? 

Answer: Sorry cat lovers — about 20 percent of the population has pet allergies, and cats are the worst offenders. In fact, cat allergies are twice as common as dog allergies. As I explained in an Ask the Vet column a few weeks ago, there is a lot of misunderstanding and confusion about why people have allergic reactions to animals. 

Allergies to cats (and other mammals) are triggered by various protein molecules, referred to as "allergens." The immune system of an allergic individual overreacts to the harmless proteins, mistaking them for dangerous substances and releasing achemical called histamine. (My apologies to allergy sufferers for this very simplistic explanation!). Allergic reactions can manifest in skin rashes, hives, sneezing, coughing, runny nose, red and itchy eyes, asthma and more. 

For many years, people thought that a cat's fur was the allergy trigger. However, as with dogs, fur is not an allergen. There are at least five cat allergens, and more have recently been discovered. But the Fel d 1 and the Fel d 4 proteins cause the majority of allergic reactions in humans. The Fel d 1 comes mainly from the sebaceous glands under the cat’s skin, the anal glands and saliva, while the Fel d 4 is found in the cat’s saliva and urine. Cat allergens are more potent than a dog’s and can remain “active” for a long time. 

When a cat grooms with his tongue, the Fel d 1 and Fel d 4 protein in the saliva covers his fur and skin. Fel d 1 secretions from the cat’s sebaceous and anal glands also land on the fur and skin. When the dead skin cells (called dander) and loose fur are released into the environment, the Fel d 1 and Fel d 4 allergens are spread. Dogs also have allergens in their saliva that are distributed by dander, but they do not lick themselves as much as cats, and their sebaceous glands are not as active.

Cat allergen dander particles are much smaller, lighter and stickier than those from a dog. In fact, they are only one tenth the size of a dust mite particle! As a result, they can remain airborne for long periods of time and travel great distances. The invisible allergens make their way easily into the respiratory passages of humans, and can stick to any surface.

Studies have shown that male cats produce more allergenic secretions than females, and that “intact” males generate more allergens than neutered males. Some people think that light-colored cats are less allergenic than dark colored cats, but there is no research to back up the theory. Since kittens have less allergens than adult cats, pet owners don’t always develop allergic symptoms until their cat reaches maturity.

Despite the negative statistics about cat allergens, many allergic pet owners still choose to live with their feline friends (including my wife!).  An estimated 6 million Americans are allergic to cats and over one third of them continue to have cats in their homes. Scientific studies show that steps can be taken to significantly decrease one's exposure to cat allergens. See my last Ask the Vet answer about reducing allergens on yourself, on your pet and in your house. 

Here are a few additional things you can do to alleviate or lessen cat allergens:

• If possible, bathe your cat once a week with a good pet shampoo or plain water. Studies have shown that a weekly bath or a water-only rinse can significantly reduce allergens. Of course, this can sometimes be a challenging task! If you begin bathing your cat at a young age, it is much easier for them to accept it. Pet Place offers some helpful cat bathing instructions.  
• Wipe your cat frequently with a cloth moistened with water or a special allergen neutralizing solution like Allerpet C. Cats that hate baths will usually tolerate a damp “wipe down.” 
• Brush your cat frequently to remove loose dander and fur. A cat’s fur, no matter what the length, can trap cat allergens along with additional environmental allergens like dust mites, mold, pollen, etc. Always do the brushing outside and wear a face mask if you’re allergic. Furminator deshedding tools are invaluable aids and well-worth the price.
• Feed your cat a high-quality food, rich in skin-supporting oils with the correct balance of Omega-3 and Omega-6 fatty acids. Cats with unhealthy skin shed more dander. Talk with your veterinarian about what food would be best for your cat.  
• Clean your cat’s little box frequently, and avoid stirring up litter dust. Keep the litter box away from air ducts – especially intake vents. If an allergic person has to change the litter, consider a self-cleaning litter box like Scoop-Free  or Litter Robot. 

For more in-depth advice please consult your veterinarian and/or human allergist. The Avoid Nasal Allergies website and the American Academy of Allergy, Asthma, and Immunology website both offer a wealth of information for those with pet allergies.  

Do you have a question for Dr. Tate? Email your questions to Webster Groves Patch Editor Sheri Gassaway. Be sure to attach a photo of your pet, and we'll feature it along with your question!