Scientists have discovered how allergic reactions to cats are triggered, raising hopes of preventative medicine.
A University of Cambridge team has identified how the body's immune system detects cat allergen, leading to symptoms such as coughing and sneezing.
New treatments to block this pathway raise hopes of developing medicines to protect sufferers, they say.
Allergy UK says the research is "a big step forward" in understanding how cat allergen causes allergic reactions.
Researchers led by Dr Clare Bryant of the University of Cambridge studied proteins found in particles of cat skin, known as cat dander, which is the most common cause of cat allergy.
They found that cat allergen activates a specific pathway in the body, once in the presence of a common bacterial toxin.
This triggers a large immune response in allergy sufferers, causing symptoms such as coughing, wheezing, sneezing and a runny nose.
Dr Bryant told BBC News: "We've discovered how the cat allergy proteins activate the host immune cells.
"By understanding the triggering mechanism, there are now drugs that have been designed that are in clinical trials for other conditions, such as sepsis, that could potentially then be used in a different way to treat cat allergy and to prevent cat allergy."
The charity Allergy UK said the research, published in Journal of Immunology, was a big step forward in understanding how cat allergen causes such severe allergic reactions.
"Cat allergen is particularly difficult to avoid as it is a 'sticky' molecule that is carried into every building on people's shoes and clothes," said director of clinical services Maureen Jenkins.
"It can also still be found in a home, on the walls and ceiling or fittings, even a few years after a cat has ceased to live there.
"Therefore, this new information identifying the specific receptor interaction in the immune system could pave the way for treatments for those with persistent disease triggered by cat allergen and, in the future, potentially dog and house dust mite allergen."
Allergic reactions happen when the immune system overreacts to a perceived danger.
Instead of responding to a harmful virus or bacteria, it misidentifies allergens, such as cat dander, and mounts an immune response.
The research was funded by the Wellcome Trust and the Medical Research Council.