Allergy to cats

Type of animal allergy caused by felines

Allergies to cats, a type of animal allergy, are one of the most common allergies experienced by humans. Among the eight known cat allergens, the most prominent allergen is secretoglobin Fel d 1, which is produced in the anal glands, salivary glands, and, mainly, in sebaceous glands of cats, and is ubiquitous in the United States, even in households without cats. The second most common is Fel d 2, this type is triggered by the cats dead skin flakes (dander) that are floating in the air as well as in the smell of cat urine. Allergic symptoms associated with cats include coughing, wheezing, chest tightening, itching, nasal congestion, rash, watery eyes, sneezing, chapped lips, and similar symptoms. In worst case scenarios, allergies to cats can develop into severe respiratory symptoms such as rhinitis and mild to severe forms of asthma. The remaining cat allergens are Fel d 2–8, with Fel d 4, a major urinary protein found in the saliva of cats, occurring the most in humans among the other seven allergens. All cats produce Fel d 1, including hypoallergenic cats. The main method of transmission is through a cat's saliva or dander, which adheres to clothing. A 2004 study found that 63% of people allergic to cats had antibodies against Fel d 4.

Fel d 4 and Fel d 7 are cat lipocalins. Fel d 4 and Fel d 7 are two of the most common cat allergens after Fel d 1. Fel d 4 is produced in the submandibular salivary glands and is secreted in the saliva of cats, via which it is deposited on to cat dander during grooming, hives or rash on the face or chest; and itchy skin. If a cat has scratched, licked, or bitten someone who is allergic to cats, redness and sometimes even swelling of the affected area will occur. For those severely allergic, symptoms may include airway swelling such as in anaphylaxis, thereby requiring urgent medical attention. Depending on the person, an allergic reaction to cats can trigger other underlying disorders, such as asthma or atopic dermatitis (eczema).

As the allergen enters through the nose or mouth, antigen presenting cells of the innate immune system analyze the allergen and present antigenic peptides to helper T cells. In its early stages, AIT utilized cat dander extract, which consists of microscopic dry skin flakes of cats, but later resorted to Fel d 1 due to issues of standardization. One way researchers use Fel d 1 in immunotherapy is through the alteration of its chemical structure. Disulfide bonds between Fel d 1 chains were broken to reduce the binding between the allergen and immunoglobulin E (IgE), inhibiting an allergic response.

Regularly bathing a cat may remove significant amounts of allergens from fur. After bathing, the levels of Fel d 1 on cat skin and fur return within two days of bathing. In addition, amounts of Fel d 1 in the surrounding air return after a 24 hour period of bathing the cat. and Cat SPIRE. As of 2019, the Swiss company HypoPet AG is developing a vaccine it hopes could be administered to cats to reduce the emission of Fel d 1 proteins. More recently, in 2022 at the National Institute of Health they conducted an experiment with allergy shots and a monoclonal antibody Tezepelumab. Among the tests, the participants given the shot with the Tezepelumab had greater results than the placebo group and the single allergy shot.

Cat food containing the anti Fel d 1 IgY antibody found in eggs has been found to reduce Fel d 1 levels in fur.

A hypoallergenic cat is a cat that is less likely to provoke an allergic reaction in humans. Although the topic is controversial, owners' experiences and clinical studies suggest that Siberian cats, Devon Rex and Cornish Rex cats, Abyssinian cats, Balinese cats, and several other breeds, especially females, are likely to have low levels of Fel d 1, the main allergenic protein. From among the above cats noted, the most popular cat breeds to be renowned for their hypoallergenic quality are the Siberian and Balinese. These cats produce much fewer protein allergens in comparison to regular domestic household cats or other cat breeds. Cats that have some Balinese ancestry might produce lower amounts of protein allergens. Cat breeds that often have some Balinese lineage include the Oriental Shorthair, Oriental Longhair, and some Siamese cats. The common theory among these two hypoallergenic medium to long haired cat breeds is that their long haired gene is associated with producing reduced amounts of allergens. This may be the case as the Balinese cat, a medium to long haired cat breed (also referred to as the Long haired Siamese cat) is regarded as hypoallergenic, whereas the Siamese cat, a short haired breed, is not. Some Siamese cats might possess hypoallergenic qualities if they have Balinese ancestry. This might provide some evidence that the long haired genes or traits within this cat breed have resulted in a cat that can genetically produce less amounts of the cat allergens. 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 announced that on 1 January 2010, they will cease their breeding activities. In 2006, another company, Felix Pets, also claimed to be developing a breed of hypoallergenic cat.

Female cats (unspayed or spayed) produce a lower level of allergens than males, and neutered males produce a lower level of allergens than unneutered 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.