Chemicals that naturally occur in human skin could render people invisible to mosquitoes, researchers say, and may lead to an alternative to current repellant options. Scientists tested various compounds and found that some blocked the bugs' sense of smell. "We are exploring a different approach, with substances that impair the mosquito's sense of smell. If a mosquito can't sense that dinner is ready, there will be no buzzing, no landing and no bite," said Department of Agriculture researcher Ulrich Bernier.