NEXT TIME YOU'RE TEMPTED TO think your job bites, consider the plight of Nigel Hill. For the past five years, the British entomologist has unflinchingly bared his forearms, and sometimes his shins, for the dining delectation of hungry mosquitoes—often enduring 400 nips a day. "I love my job," says Hill, head technologist at the London School of Hygiene & Tropical Medicine, whose work is aimed at fighting such deadly insect-borne diseases as malaria. "Mosquitoes are a huge killer," he says. "We're trying to save 2 to 3 million lives a year." High-minded though his goals may be, he admits he looks forward to receiving his last bite of the day—after which he celebrates with a "damn good scratch."

It was an itch for science that initially brought Hill, now 35, to the school at age 16. He literally began at the bottom, learning how to breed mosquitoes in the building's clammy converted coal cellars. Nowadays, Hill, who earned a bachelor's degree in life sciences in 1986, delegates that duty to two underlings. His own responsibilities include frequent field trips to Africa, Asia and South America but mostly offering himself up to hordes of minute marauders to test the efficacy of various repellents. (Corporate-funded trials of First World consumer products help bankroll the Third World work.) "I've fed so many millions of mosquitoes that my immune system acts instantaneously," says Hill, whose flesh is typically a welter of red lumps. "But within an hour they're gone." Until then, he says, plain cold water works just fine to soothe the irritation.

The researcher's wife, Theresa, 34, understands his odd job better than most would; she's a microbiologist. But she does draw a line. "I have to be reminded if we are going out," says Hill, referring to his mosquito-ravaged arms. "For special occasions I put on long sleeves to avoid startling people."