It's a cruel fact of life that many cat lovers suffer from an allergy to the very creatures they adore. But rather than be relegated to a life devoid of felines (or suffer from sneezing and itchy eyes whenever a cat is near), allergy sufferers may soon be able to enjoy the company of their furry friends without any ill effects.

The Protein Responsible for Cat Allergies

Scientists have long known about the existence of a certain protein, known as the Fel d 1 protein, that is responsible for most severe allergic reactions to cats. The protein is found in cat dander, which is comprised of microscopic pieces of dried skin mixed with dried saliva. But a team at the University of Cambridge in England recently unlocked the mystery of how exactly Fel d 1 causes such unpleasant reactions in susceptible humans.

The team found that the reactions are generated not directly by the dander, but by the presence of a common environmental toxin known as lipopolysaccharide (LPS). It appears that LPS acts as a trigger for the allergic reaction to the dander to take place.

The scientists conducted a series of tests in which human cells were exposed to cat and dog dander when LPS was present and again when it was absent. LPS, even in tiny amounts, led to a significant allergic response. "LPS is present all over the place in surprisingly large amounts, so it is unlikely one would ever encounter cat allergen that was free of LPS," says Clare Bryant, DVM, professor of innate immunity at the Department of Veterinary Medicine at the University of Cambridge. Translation? If there's a cat nearby, there will almost certainly be a reaction in someone who has an allergy.

Promising New Developments in Preventing Cat Allergies

That may soon change, however, as the Cambridge scientists were able to identify the specific immune-system receptor that responds to LPS, called Toll-like receptor 4 (TLR4). When they administered a drug that tamps down the TLR4 response in the human cells, they discovered that the allergic response to cat dander was also inhibited.

Since drugs that quiet the TLR4 response already exist, Bryant and her team are hopeful that there will be new developments in treating cat allergies and, possibly, dog allergies as well.

Clare Bryant reviewed this article.


Clare Bryant, professor of innate immunity at the Department of Veterinary Medicine at the University of Cambridge, England. E-mail exchange with author, December 15-16, 2013

University of Cambridge,, accessed December 15, 2013.