By Caroline Ryan
BBC News Online health staff
The immune system - often seen as the enemy in severe allergic reactions - could be harnessed to fight them, scientists have suggested.
The proteins could help people with cat allergies
For most people with allergies, the only options are to stay away from the allergens which trigger reactions - such as cats - or take medications to ward off symptoms. such as hay fever treatments.
But growing knowledge about proteins called toll-like receptors (TLRs) could mean it would be possible to train the immune system not to react against the allergen.
The body has two types of immune response, one to allergies and one to inflammation. If the body could be taught to respond with an inflammatory response to an allergen, it could reduce sufferers' coughs and sneezes.
TLRs were first seen in fruit-flies. They get their name because the German researcher who first spotted them shouted "toll" - German for great.
TLRs sit on the surface of certain immune cells.
They send out a message to tell the immune system an infection is present and can send other cells in the immune system to attack it.
Scientists believe this role could be harnessed to treat allergies.
TLRs tend to prompt the immune system to respond to infectious agents like bacteria and viruses - not allergens.
Dr Ian Sabroe, is a chest physician at the Royal Hallamshire Hospital, Sheffield, who has been looking at the role of TLRs in infections and controlling allergies.
He told BBC News Online: "TLR signals have the potential to drive the immune system away from the allergic response towards responses that are more effective at killing bugs.
"This may have the benefit of down-regulating allergic disease.
"It may be possible to use TLR signals to enhance immunity , for example with vaccines, or to persuade the immune system to react to things in a way less associated with allergy.
"Thus, TLR signals present at the same time as an allergen might help prevent the development of allergic responses, or alternatively help suppress them in someone with established allergy."
He added it was already possible to give people with some allergies desensitisation treatment in a bid to change the way their bodies react to allergens, but that was done via many injections over a few years.
But he added: "We could change the immune system to stop the allergic response."