What Is Cat Dander?

Person and cats lounging on couch

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While cat dander remains a mystery to some people, it poses a concern to those who suffer from allergies. Here are the details on what exactly is cat dander, the mystery of Fel D1, and how and why it affects allergy victims.

For years, it was thought by many people that cat hair was the source of allergens. Later, it was recognized that cat dander was the cause, but many cat lovers confused the term with dandruff, which is visible to the eye.

Cat dander consists of microscopic pieces of dry cat skin that become airborne, landing on bedding, curtains, carpeting, and other surfaces, including humans' skin and clothing. Cat dander particles are tiny, about 1/10th the size of dust mites. Dry skin particles wouldn't be particularly allergenic except for a factor known as Fel D1. 

What Is Fel D1?

Fel D1 may come from the Latin Felis domestica. It is a glycoprotein found in the cat's sebaceous glands under the skin, and to a lesser degree in cats' saliva and urine. When a cat grooms their coat, the Fel D1 present in their saliva lands on the cats' skin and hairs, and, combined with the Fel D1 from the sebaceous glands, creates a sort of "double-whammy" to allergy sufferers. Interestingly, the production of Fel D1 appears to be more or less prolific in different types of cats.

Whole cats, for example, will produce more Fel D1 than a neutered cat would. Male cats, particularly unaltered ones, produce more allergens than female cats. Some cat breeds produce substantially less Fel D1 than others.

What Causes the Allergic Reaction to Cat Dander

When challenged by an allergen, people's immune systems consider the allergen to be an invader and produce an antibody called immunoglobulin E ( AKA IgE).

Thereafter, when exposed again to Fel D1, the immune system is launched, which then releases an inflammatory chemical known as histamine. You may recognize the term "histamine" because of the huge number of antihistamines sold over the counter to treat hay fever symptoms.

How Fel D1 Affects People

  • Inhaled through the nose: The allergic reaction may be violent sneezing and or the chronic condition called allergic rhinitis, also known as "hay fever," which manifests with sneezing, accompanied by a runny nose, itching inside the nose, nasal congestion, and sometimes sinus congestion.
  • Inhaled through the mouth: Dander inhaled into the bronchial tubes and the lungs can trigger asthma attacks, which are uncomfortable and even dangerous. Asthma sufferers should always consult with their allergists and should undergo allergy testing before getting a cat. According to the American Academy of Pediatrics, studies suggest up to 40 percent of children and young adults with asthma are allergic to animal dander (primarily cats). For more information, check out the American Academy of Allergy, Asthma, and Immunology.
  • Skin rash or hives: Minor skin rashes or hives may be associated with dander falling on the skin, saliva deposited by a cat licking the skin, or even through inhaling the dander. Atopic dermatitis or eczema may be exacerbated by exposure to cats.

Although cat dander is a real threat to allergy victims, some cat lovers are able to cope with their allergies well enough to live in relative comfort with their cats. Let your own allergist be the judge of this and follow their advice.

Article Sources
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  1. Pet Allergy. American Academy of Allergy, Asthma and Immunology.

  2. Bastien BC, Gardner C, Satyaraj E. Influence of time and phenotype on salivary Fel d1 in domestic shorthair cats. J Feline Med Surg., vol. 10, pp. 867-874, 2019. doi:10.1177/1098612X19850973

  3. Hay Fever (Rhinitis) Symptoms. American College of Allergy, Asthma & Immunology, June 2020.

  4. Cats and Children with Asthma. American Academy of Pediatrics.

  5. Schneider, Lynda. Eczema, Atopic Dermatitis and Allergies: What Is The Connection? National Eczema Association, July 2021.