Scientists say they have developed a technique which could prevent allergies caused by cats.
Cat allergen particles are easily inhaled
In the UK, pets are the second most important cause of allergy in the home, and 50% of asthmatic children are allergic to cats.
The University of California, Los Angeles, team combined a fragment of a human protein with a cat allergen.
Nature Medicine reports mice treated with the fused protein did not develop allergic responses.
Cat allergen is present on very small particles that readily become airborne when disturbed and are easily inhaled.
When a person experiences an allergic response, a chemical called IgE, produced by the immune system in response to the presence of allergens such as cat hair, binds to specific receptors on the surface of immune cells.
This triggers the release of histamine in tissues in the body, causing symptoms such as itching, sneezing and a runny eyes and nose.
Other immune-based therapies rely on frequent injections of allergens, with the dose being gradually increased each time.
But this is a time-consuming process, which can cause serious reactions in patients.
The researchers were looking at ways of preventing the allergic response and histamine production.
They were able to combine part of human immunoglobulin (IgG), a protein which blocks allergic reactions, with a piece of cat allergen.
The fused protein connected with the IgG receptor on the surface of the immune cell, telling it not to "explode" and release histamine.
It meant that this "stop" message was stronger than the "go" message, which was created by the presence of the allergen in the body.
However, the immune system is still being exposed to the allergen, so although it would still recognise it in future, it would be "retrained" not to see it as something it should have an allergic response to.
Tests on mice showed those treated with the fusion protein did not develop allergic airway inflammation in response to cat allergen.
Researcher Dr Andrew Saxon said: "We wanted to create a system that would prevent you from getting sick when you were exposed to an allergen, but which could also be used to retrain the immune system in the long run.
"We could use the same technique to target other allergies, including peanut."
Philippa Major, assistant director of research at Asthma UK said: "This is an interesting study but is still in the early stages of development as no human studies have begun.
"This approach taken by the UCLA group does not modify the T cell response and therefore the treatment would need to be administered on a continuous basis to prevent symptoms .
"Currently a different, and potentially long term prevention approach of a T cell vaccine for people with cat allergy is being developed by Asthma UK research fellow Dr Mark Larché."