Cat Allergen Fel D1

by Michael
(London, UK)

3D rendering of the Fel d 1 dimer, the primary allergen present in cat saliva – Wikimedia commons file

This is reverse cat health. It’s about human health problems caused by a cat. It is a Wikipedia article extended and reworked (and reproduced under their license) to make it a bit more readable (hopefully!) and more complete on one page.

The Fel d 1 protein, produced largely by cat saliva and sebaceous glands, is the primary allergen present on cats. Atopy is a disease characterized by a tendency to be “hyperallergic”.

Definitions for para above:

Fel D1: Believed to stand for: Felis Domesticus 1 (1 being the first allergen discovered).

protein: a class of molecule that are organic compounds made of amino acids arranged in a linear chain and folded into a globular form.

saliva: the watery and usually frothy substance produced in the mouths of humans and most other animals.

sebaceous glands: microscopic glands in the skin which secrete an oily/waxy matter, called sebum, to lubricate the skin and hair of mammals.

allergen in cats: a nonparasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals.

Atopic individuals: Most humans mount significant Immunoglobulin E (IgE) responses only as a defense against parasitic infections. However, some individuals mount an IgE response against common environmental antigens. This hereditory predisposition is called atopy. In atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity. Sensitivities vary from one person to another and it is possible to be allergic to an extraordinary range of substances.

The protein is of an unknown function to the animal but causes an IgG or IgE reaction in sensitive humans (either as an allergic or asthmatic response). Removal of soft surfaces in the home (carpet, furniture), frequent washings of bed linens, HEPA filters and even washing cats have been proven to reduce the amounts of Fel d 1 present in the home. Fel d 1 is a particularly sticky protein and has been shown to cling to clothing and human hair and can be detected in environments where a cat has never been present.

Definitions for para above:

IgG antibodies: are produced for several hours/days after exposure to an allergen. They are called Type III delayed hypersensitivity reactions. IgG antibodies are predominately involved in the secondary immune response.

IgE antibodies: is a class of antibody that has only been found in mammals. It plays an important role in allergy, and is especially associated with type 1 hypersensitivity. It has also been implicated in immune system responses to most parasitic worms.

Cats produce, on average, 2-7 µg of Fel d 1 per day. Studies have shown that intact males produce Fel d 1 in levels higher than castrated males, leading to the assumption that Fel d 1 is hormonally regulated by testosterone. Castrated males produce Fel d 1 in levels similar to females (both intact and altered females produce Fel d 1 in similar levels). Even though females and castrated males produce Fel d 1 in lower levels, they still produce enough to cause allergic symptoms in sensitive individuals.

Definitions for para above:

µg: a microgram (µg , mcg or sometimes ug) is a unit of mass equal to 1/1,000,000 of a gram.

Fel d 1 is an 18 kDa heterodimer protein and belongs to the secretoglobin family of small disulfide linked dimeric proteins found only in mammals.

Update July 2012: A cat’s allergen is twice as likely to cause an allergic reaction that a dog’s allergens because it smaller and stickier. It can remain airborne for hours and sticks to surfaces. Its size is ideal for inhaling into a person’s lungs (src: Mark Larché, an immunology professor at McMaster University in Ontario).

Read more:

Cat Allergen Fel D1 to Cat Health Problems

Comments for
Cat Allergen Fel D1

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Dec 11, 2011New allergen inactivation wipe and spray FOR CAT ALLERGY
by: Anonymous

Dr C Steven Smith, an allergist in Louisville Ky. has developed a immunologically proven way to keep pets and minimize the allergy symptoms they may cause. The patented product is called Solunogen and may be purchased at a very reasonable price from Feeder’s Supply in Louisville, or from his office at 1017 Dupont Sq North 40207, www.DRSMITHALLERGY.COM.


Sep 26, 2011HEY AUGUST 2nd writer
by: Anonymous

Did you ever find anything out????? I think it is possible! I have the exact same problem after a cat came to my apt! SO MAD! need a cure!

Jan 20, 2011Update jan 2011
by: Michael

I found this on Google Scholar. It is pure advanced chemistry so you’ll have to be a scientist to understand it but I have provided definitions.

Amino acid sequence of cat allergen Fel d1

Aug 11, 2010friend visiting
by: Anonymous

Your friend might want to try an anti-allergy medicine. I have found the long-lasting (24 hr) medicine is the best (Claritin or Zurtec). Do not vacumn immediately before your friend’s arrival because that just sturs up the dander. Also, an air purifier might help.

Aug 03, 2010Response
by: Michael

Hi, I think it might be possible to suddenly become allergic to cats. It may be caused by a gradual sensitisation. Some cats are much more prone to create an allergic reaction. I have never been allergic to cats but a stray that I feed makes me itch even if he is simply in the room! I have to wash hands after I pick him up.

Perhaps all of us are at least potentially allergic to cats and if we are predisposed but not yet allergic perhaps over time there is a gradual sensitisation to the allergen as can happen when handling chemicals for a long time.

I can understand that a reaction can cause breathing problems. I don’t know what to take but I would expect it to me an anti-inflammatory drug or an ant-histamine type drug (the same as is taken for hay fever). But you’ll need to check that out.

Aug 02, 2010Skin rash from Fel d 1?
by: Anonymous

I have had cats my entire life and never had an allergic reaction from them. Two years ago I suddenly developed a severe rash on the palms of both hands. The rash itches and has blisters.

My dermatoligist says it is contact dermatitis, and could be from just about anything. Is it possible to suddenly become allergic to my cats?
Maybe the Fel d 1 protein is causing a reaction, I don’t know.

Does anyone else out there have this problem? If so, is there any way to get rid of this rash? It is getting very severe.

Jul 20, 2010Help
by: Mike

Thank you for information. I have a friend that wants to come and visit me, but I have two cats, male and female both hav been spaded.

My friend said that he closes up and can’t breath even with them in the room, can he talk anyting for this.

I hope you can help me

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Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in a many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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