Fact vs Fiction

fel d 1 image

There are many myths and misconceptions related to cat allergens and many people who suffer from cat allergies do not fully understand the actual cause of their allergy.

Discover the scientific facts that dispel the popular beliefs concerning allergies to cats.

Facts about allergies to cats



Contrary to popular belief, it is not the cat’s hair that causes an allergic reaction. Allergens produced in the cat’s salivary and sebaceous (skin) glands are responsible for triggering a reaction in allergic individuals…



There is a common belief that some breeds of cats – especially the hairless breeds – are “hypoallergenic.” While “hypoallergenic” technically means “less allergenic,” many people use it to imply “allergen-free”…



A myth exists that suggests cats with darker colored hair and those with longer hair are more likely to trigger allergies than cats with lighter colored or shorter hair. However, hair color and length have no influence…



While studies have demonstrated that hair length and color have no influence on Fel d 1 production, there is one physical factor that does appear to correlate: sex…



The most common recommendation for allergy sufferers is to avoid the allergen. For this reason, physicians and allergists often recommend removing the cat from the home or, at a minimum, exclude the cat from the main living areas of the home.1,2


The Purina Institute provides the scientific facts to create awareness and clarify potential misunderstandings. Please see below for more.


Q&A on Fel d 1 and allergies to cats

How did Fel d 1 get its name?

When Fel d 1 was first discovered, the proposed name was “cat allergen 1.” The name Fel d 1 comes from Felis domesticus, which was the commonly used species name of the domestic cat at the time the allergen was officially named.  Although the domestic cat’s official species name is now Felis catus, the Fel d name has not been changed. The Fel d allergens were numbered in order of their discovery; Fel d 1 was the first.

Do all cats produce Fel d 1?

All cats produce Fel d 1 regardless of their physical characteristics.1-3 Fel d 1 levels vary widely across individual cats.4,5 Fel d 1 is produced primarily in the salivary and sebaceous glands of the cat.1,5-7 This means that even hairless cats, like the Cornish Rex and Sphinx, produce allergens.

Do cat breeds produce different levels of Fel d 1?

The production of Fel d 1 may vary somewhat by breed, but all cats produce Fel d 1. There is wide variation among individual cats regardless of breed and there are no truly hypoallergenic or allergen-free cat breeds.

Is Fel d 1 production influenced by a cat’s genetics?

Yes, as with all proteins produced by the body, Fel d 1 production is controlled by the genetic makeup of a cat.8

Does hair color or length influence Fel d 1 production?

Neither hair color nor hair length influences Fel d 1 production.2-4,9

Does body weight influence Fel d 1 production?

Body weight does not influence Fel d 1 production.2

Do cats that spend time outside produce more allergens than “indoor only” cats?

Neither indoor nor outdoor lifestyle influences Fel d 1 production.2

Are there “hypoallergenic” cat breeds?

There are no truly allergen free, or “hypoallergenic,” cats.1-2,10-11 While “hypoallergenic” technically means “less allergenic,” many people use it to imply “allergen-free.” All cats produce allergens,2,7,10  even hairless cats (e.g. Cornish Rex and Sphynx) and all cats groom themselves, dispersing dander, hair and allergens into the environment.

Does age influence Fel d 1 production?

Studies determining the relationship between age and Fel d 1 production have produced inconsistent results.3,4 A Purina study found that older cats tended to have lower salivary Fel d 1 levels than younger cats.4

Does sex influence Fel d 1 production?

Studies have shown that intact male cats generally produce higher levels of Fel d 1 than sterilized/neutered male cats and female cats regardless of sterilization status.2,9,12-14  However, each cat’s production of Fel d 1 varies based on genetics, and an intact male cat could potentially produce less Fel d 1 than a high producing female or sterilized male cat.13,14

What is the function of Fel d 1 for the cat?

The exact function of Fel d 1 in cats is still unknown, but proposed roles include pheromone signaling.15,16

Cats produce varying levels of Fel d 1 depending on neuter status, sex and genetics2,7,8 and can be healthy regardless of the level of Fel d 1 they produce.

How common are allergies to cats, and what are the consequences of these allergies?

Allergy to cats is the most common animal-origin allergy and the second most common indoor allergy in humans.17-19 Cat allergy can be a huge barrier to cat ownership20, and may limit the loving interactions between cat lovers and cats. Globally, as many as one in five adults (22 percent) have a response to cat allergens.16,21

What causes allergies to cats?

When most people have an allergic reaction to cats, they are usually responding to one allergen in particular known as Fel d 1.16,18  Fel d 1 is the major cat allergen, causing allergic reactions in up to 95 percent of cat allergen-sensitized individuals.9,16-18,22 It is primarily produced in the salivary and sebaceous (skin) glands of cats.1,3,6,7,9,22

These allergens are transferred to a cat’s hair and skin during grooming, which then can be dispersed on dander (dried flakes of skin) and hair around the home.6,7,16 House dust may contain high concentrations of the Fel d 1 allergen.19 Fel d 1 easily becomes airborne, and lingers in the environment; it is also easily transported on clothing to other environments without cats (such as car interiors, classrooms, shopping centers, etc.).9,11,16 The allergic response begins when Fel d 1 binds with the immunoglobulin E (IgE) in a sensitized person's body and triggers the allergic response.

How are allergies to cats usually managed?

Current methods for managing human allergies to cats focus on limiting or avoiding exposure to cats, intensive cleaning, desensitizing the allergic individual through immunotherapy, or treating the symptoms of the allergic response once triggered.10,11,23 Each of these approaches has limitations.

Related content

Find out more about this discovery, and what this could mean for the lives of cats and the people who care for them:

Find out more

1. Butt, A., Rashid, D., & Lockey, R. (2012). Do hypoallergenic cats and dogs exist?  Annals of Allergy Asthma and Immunology, 108(2), 74-76. doi: 10.1016/j.anai.2011.12.005

2. Nicholas, C., Wegienka, G., & Havstad, S. (2008). Influence of cat characteristics on Fel d 1 levels in homes. Annals of Allergy Asthma and Immunology, 101(1), 47-50. doi: 10.1016/S1081-1206(10)60834-4

3. Kelly, S.M., Karsh, J., Marcelo, J., Boeckh, D., Stepner, N., Litt, D.,...Yang, W.H. (2018). Fel d 1 and Fel d4 levels in cat fur, saliva and urine. Journal of Allergy and Clinical Immunology, 142, 1990-1992.e3. doi:  10.1016/j.jaci.2018.07.033

4. Bastien, B.C., Gardner, C., Satyaraj, E. (2019). Wide range of yearly salivary Fel d 1 in domestic shorthair cats. Accepted, Journal of Feline Medicine and Surgery.

5. Platts-Mills, T.A.E., Vervioet, D., Thomas, W.R., Aalberse, R.C., & Chapman, M.D. (1997). Indoor allergens and asthma: Report of the Third International Workshop. Journal of Allergy and Clinical Immunology, 100, S1-S24.

6. Dabrowski, A., Van der Brempt, X., Soler, M., Seguret, N., Lucciani, P., Charpin, D., & Vervloet, D. (1990). Cat skin as an important source of Fel d 1 allergen. Journal of Allergy and Clinical Immunology, 86, 462-465.

7. Bartholome, K., Kissler, W., Baer, H., Kopietz-Schulte E., & Wahn, U. (1985). Where does cat allergen 1 come from? Journal of Allergy and Clinical Immunology, 76, 503-506. doi: 10.1016/0091-6749(85)90734-1

8. Morgenstern, J.P., Griffith, I.J., Brauer, A.W., Rogers, B.L., Bond, J.F., Chapman, M.D., & Kuo, M.C. (1991). Amino acid sequence of Fel dI, the major allergen of the domestic cat: Protein sequence analysis and cDNA cloning. Proceedings of the National Academy of Sciences, 88(21), 9690-9694.

9. Bonnet, B., Messaoudi, K., Jacomet, F., Michaud, E., Fauquert, J.L., Caillaud, D., & Evrard, B. (2018). An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen. Allergy Asthma & Clinical Immunology, 14. doi: 10.1186/s13223-018-0239-8

10. Dávila, I., Dominguez-Ortega, J., Navarro-Pulido, A., Alonso, A., Antolin-Amerigo, D., Gonzalez-Mancebo, E.,…Torrecillas, M. (2018). Consensus document on dog and cat allergy. Allergy, 73, 1206-1222. doi: 10.1111/all.13391

11. Salo, P.M., Cohn, R.D., & Zeldin, D.C. (2018). Bedroom allergen exposure beyond house dust mites. Current Allergy and Asthma Reports, 18, 52-68. doi: 10.1007/s11882-018-0805-7

12. Zielonka, T., Charpin, D., Berbis, P., Luciani, P., Cassanova, D., & Vervloet, D. (1994). Effects of castration and testosterone on Fel d 1 production by sebaceous glands of male cats: I. Immunological assessment. Clinical and Experimental Allergy, 24(12), 1169-1173.

13. Ramadour, M., Birbnaum, J., Magalon, C., Lanteaume, A., Charpin, D., & Vervloet, D. (1998). Cat sex differences in major allergen production (Fel d 1). Journal of Allergy and Clinical Immunology. 10(2-1), 282-284.

14. Jalil-Colome, J., de Andrade, A.D., Birnbaum, J., Casanova, D., Mége, J.L., Lanteaume, A., Charpin, D., & Vervloet, D. (1996). Sex difference in Fel d 1 allergen production. Journal of Allergy and Clinical Immunology, 98(1), 165-168.

15. Durairaj, R., Pageat, P., & Bienboire-Frosini, C. (2018). Another cat and mouse game: deciphering the evolution of the SCGB superfamily and exploring the molecular singularity of major cat allergen Fel d 1 and mouse ABP using computational approaches. PLoS ONE, 13(5), e0197618; doi: 10.1371/journal.pone.0197618

16. Zahradnik, E., & Raulf, M. (2017). Respiratory allergens from furred mammals: Environmental and occupational exposure. Veterinary Sciences, 4(3), 38. doi: 10.3390/vetsci4030038.

17. Morris, D. (2010). Human allergy to environmental pet danders: A public health perspective. Veterinary Dermatology, 21(5), 441-449. doi:10.1111/j.1365-3164.2010.00882.x

18. van Ree, R., van Leeuwen, W., Bulder, I., Bond, J., & Aalberse, R. (1999). Purified natural and recombinant Fel d 1 and cat albumin in vitro diagnostics for cat allergy. Journal of Allergy and Clinical Immunology, 104(6), 1223-1230.

19. Black, K.R., Murphy, B., Filep, S., Brook, J., Subbarao, P., Turvey, S., … Chapman, M.D. (2018). Comparison of Fel d 1 and Fel d4 levels in house dust samples from the Canadian CHILD birth cohort. Journal of Allergy and Clinical Immunology, 141(2), AB7.

20. Svanes, C., Zock, J.P., Anto, J., Dharmage, S., Norback, D., Wjst, M., … Early Life Working Group of the European Community Respiratory Health Survey. (2006). Do asthma and allergy influence subsequent pet keeping? An analysis of childhood and adulthood. Journal of Allergy and Clinical Immunology, 118(3), 691-698. doi: 10.1016/j.jaci.2006.06.017

21. Bousquet, P.J., Chinn, S., Janson, C., Kogevinas, M., Burney, P., & Jarvis, D. (2007) European Community Respiratory Health Survey I. Geographical variation in the prevalence of positive skin tests to environmental aeroallergens in the European Community Respiratory Health Survey I. Allergy, 62(3), 301-309.

22. Chan, S.K., & Leung, D.Y.M. (2018). Dog and cat allergies: Current state of diagnostic approaches and challenges. Allergy, Asthma and Immunology Research, 10, 97-105. doi: 10.4168/aair.2018.10.2.97

23. Björnsdottir, U. S., Jakobinudottir, S., Runarsdottir, V. & Juliusson S. (2003). The effect of reducing levels of cat allergen (Fel d 1) on clinical symptoms in patients with cat allergy. Annals of Allergy, Asthma and Immunology, 91, 189-194.