Specifically, eggs from a farm where chickens and cats live together.
Its also very light and can easily travel through the air.
Studies have found this protein in homes without cats, buildings, and public transportation.

Photo Illustration by Michela Buttignol for Verywell Health; Getty Images
If you think about where you might find cat allergen, its all over the place, saidH.
James Wedner, MD, FACP, an allergy and immunology specialist at Washington University in St. Louis.
How Else Can You Cope With a Cat Allergy?
There might come a day when it’s possible for you to adopt a cat thats hypoallergenic.
We often get a lot more success when we approach things from a multi-pronged approach, Wada said.
The chickens can pass these antibodies onto their egg yolks.
If a cat is fed these eggs, it could potentially be less allergenic.
However, research on this theory is limited and involves very small sample sizes.
Sparkes AH.Human allergy to cats: a review of the impact on cat ownership and relinquishment.J Feline Med Surg.
2022;5(2):213-223. doi:10.1089/crispr.2021.0101