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Cat allergy in humans is an allergic reaction to one or more allergens produced by cats. The most common of these allergens are the glycoprotein Fel d 1, secreted by the cat's sebaceous glands and Fel d 4, which is expressed in saliva. An allergic reaction is a histamine reaction that is usually characterized by coughing, wheezing, chest tightening, itching, nasal congestion, rash, watering eyes, sneezing, chapped lips, and similar symptoms.
Five cat allergens have been described in medical literature. The two major allergens are Fel d 1 (a secretoglobin) and Fel d 4 (a lipocalin). The minor allergens include Fel d 2 (an albumin), Fel d 3 (a cystatin), and cat IgA.
Fel d 4 is the product of the cat major urinary protein gene. It is primarily expressed in the submandibular salivary gland and is deposited onto dander as the cat grooms itself. A study found that 63% of cat allergic people have antibodies against Fel d 4.
Symptoms of an allergic reaction to cats include swollen, red, itchy, and watery eyes; nasal congestion, itchy nose, sneezing, chronic sore throat or itchy throat, coughing, wheezing, asthma, hay fever, hives or rash on the face or chest, or itchy skin. If a cat has scratched, licked, or bitten someone who is allergic to cats, redness will occur. Symptoms are often confused with a common cold.
Allergens are airborne and survive for months or even years by themselves, hence removing anything that can trap and hold the allergens (carpet, rugs, pillows) and cleaning regularly and thoroughly with HEPA filters and air purifier systems reduces risk. Frequent hand washing, especially after handling the cat, and washing hands prior to touching eyes, nose, or mouth, and limiting the cat's access to certain rooms, such as the bedroom or other rooms where much time is spent, may also reduce allergic reactions.
Cat allergies can often be controlled with over the counter or prescription medications. Antihistamines and decongestants may provide allergy relief.
The Synthetic epitope vaccine is an in-development vaccine to provide a long term vaccine for allergies.
Regularly bathing the cat may remove significant amounts of allergens from the fur. Furthermore, regularly brushing the cat will reduce the amount of loose fur (and its attached saliva) in the air. Feeding the cat a high quality diet with plenty of Omega-3 fatty acids will help keep the coat healthy and minimize dander.
A hypoallergenic cat is a cat that is less likely to provoke an allergic reaction in humans. Although the topic is controversial, with many studies showing statistically significant results, owners' experience and recent clinical studies suggest that Siberian cats, Russian Blue cats, Devon Rex and Cornish Rex cats, Abyssinian cats, Balinese cats, Oriental Shorthair, and several other breeds, especially females, are likely to have low levels of Fel d 1, the main allergenic protein.
In 2006, the Allerca company announced the successful breeding of a line of hypoallergenic cats. However, no peer-reviewed studies have been done to confirm their claims and many scientists and consumers are skeptical of the company's assertions. The company has announced that on January 1, 2010 they will cease their breeding activities.
Another company, Felix Pets, also claims to be developing a breed of hypoallergenic cat.
Female cats produce a lower level of allergens than males, and neutered males produce a lower level of allergens than unaltered males. In 2000, researchers at the Long Island College Hospital found that cat owners with dark-colored cats were more likely to report allergy symptoms than those with light-colored cats. A later study by the Wellington Asthma Research Group found that fur color had no effect on how much allergen a cat produced.