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. In some severe cases, reactions may progress rapidly to cause the victim's airway to become inflamed and close up, requiring emergency medical attention. Those with severe, life-threatening cat allergies face tremendous challenges due to lack of public awareness about anaphylactic cat allergies, and do not enjoy the same conscientiousness from the public as those with a food allergy might, due to widespread knowledge of allergies to allergens such as nuts or dairy.
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 range from mild to severe, and 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 and sometimes even swelling of the affected area will occur. For those severely allergic, a reaction may resemble that of someone with a severe food allergy, and such reactions require emergency medical care.
