QuoteOver the next few years, he hopes to advance his proofs with another experiment. Sitting on a lab bench is a plastic box housing a pair of mice. There are dozens more in the basement of their building. Some of the mice are ordinary, but others have been genetically engineered to remove their ability to make IgE – so they can't get allergies.

Medzhitov will be observing these allergy-free mice for the next couple of years. The animals may be spared the misery of hay fever caused by the pollen that will inevitably drift into their box on currents of air. But Medzhitov predicts they will be worse off for it. Unable to fight allergens, they will let toxic molecules pass into their bodies, to damage organs and tissues.

If this experiment works out, it could eventually lead to dramatic changes in how allergies are treated. "It might be that completely blocking allergic defences is a bad idea, Medzhitov says. Instead, allergists should be learning why some people turn a protective response into a hypersensitive one. "It's the same as with pain," says Medzhitov. "No pain at all is deadly; normal pain is good; too much pain is bad."

For now, however, he would just be happy to get people to stop seeing allergies as a disease. "You're sneezing to protect yourself. The fact that you don't like the sneezing, that's tough luck," he says. "Evolution doesn't care how you feel."