Scientists discover what triggers allergic reactions to cats

Research conducted by a University of Cambridge team expands the possibility of creating preventative medicines

One alarmed woman rang police when her cat presented her with a bag of cannabis, leaving it on her doorstep

Scientists have discovered how allergic reactions to cats are triggered, paving the way for developing preventative treatments.

A team at the University of Cambridge looked at the way in which the body's immune system detects cat allergen, and discovered that the most common cause of severe allergic reactions are because of the Fel d 1 protein found in particles of cat skin, know as cat dander.

In a study published in the Journal of Immunology, researchers found that cat allergen activates a specific pathway receptor in the body known as Toll-like receptor 4 (TLR4) when in the presence of a common environmental bacterial toxin, LPS.

This triggers a severe immune response for those who suffer with allergies and causes common symptoms such as coughing ans sneezing.

Researchers exposed human cells to cat and dog dander proteins in the presence and in the absence of low levels of LPS. The researchers found that when LPS is present, it increases the signalling to the body’s immune system, intensifying the body’s inflammatory response to the Fel d 1 protein.

The researchers then used a drug which inhibits the TLR4 response, and found that it blocked the effects of the cat dander protein on human cells. This prevented an inflammatory response.

Now, new treatments could be developed that attempt to block this pathway and inhibit allergic reactions.

Dr Claire Bryant, lead author of the research from the University of Cambridge's Department of Veterinary Medicine said the team are hopeful that this study will lead to new and improved treatments for cat and dog allergy sufferers.

“How cat dander causes such a severe allergic reaction in some people has long been a mystery. Not only did we find out that LPS exacerbates the immune response’s reaction to cat dander, we identified the part of immune system that recognises it, the receptor TLR4," she said.

“As drugs have already been developed to inhibit the receptor TLR4, we are hopeful that our research will lead to new and improved treatments.”

Allergic reactions occur when the immune system overreacts to a perceived danger. Instead of identifying and responding to a harmful virus or bacteria, it misidentifies different allergens, including dander, as dangerous and mounts an immune response which triggers sneezing, coughing and wheezing.