This is turning the tables in a dramatic way because almost all the literature on cat allergies concerns humans being allergic to cats.
My research on the subject of cats being allergic to humans results in the conclusion that humans do not directly produce an allergen which sits on their skin or in their hair to which the domestic cat might be allergic. And neither is their anything in our breath etc. which might cause an allergic reaction in cats (unless we are exhaling cigarette smoke!).
However, humans do produce a lot of allergens that affect cats profoundly in the products that we make and use such as carpets, cleaning products, cigarette smoke, cat food, dust mites on household items and so on.
The webpages I have read on this subject refer to cats being allergic to human made products, as mentioned above, but this not the same thing. Around 10% of humans are allergic to the Fel D1 protein in cat saliva. The saliva is produced by the cat. Humans do not, themselves, produce a similar substance (or any substance for that matter) which affects cats. That is the point and that is what the question in the title is getting at.
I have read a lot of books on cats and stories from visitors over a ten year period. I have never encountered cats being allergic to humans. However, there has to be a caveat. We know cats can be allergic to substances in the human home but vets often don’t know the source of the allergy. It can be tricky to isolate the cause of an allergy in a cat; to track down the specific allergen.
Therefore it is not beyond the bounds of possibility that some cats might be allergic to their human caretaker. However, I’d speculate that it is highly unlikely and that it does not exist. With all the words written about domestic cats on the internet there would by now be something on cats being allergic to humans if this cat health problem existed. The scientific books don’t help which reinforces my thoughts. The top Google search result, the popsci.com site, suggests or speculates that a chemical on the human skin might trigger an allergic reaction in a cat but there is nothing to support this.
A vet on National Geographic.com says that feline asthma can be caused by humans but once again she is speculating. I have read her article and it is weak.
In answer to the question: What percentage of cats are allergic to humans? Google comes up with the percentage of people who are allergic to cats! That’s back to front Google. Please try and do better next time.
Please leave a comment if you think you know better.