As they reported this fall in the Journal of the American Chemical Society, the researchers discovered that the same receptors in the nose that pick up these unpleasant-smelling molecules also bind with particles of copper that reside in nasal mucus. The metallic partner amplifies a thiol's intensity by up to 1,000 times. And in experiments in which the scientists created thiol receptors that could not bind with copper, sensitivity to the odorant all but disappeared.

— Read more at Chemists Discover Why the Nose Is Hypersensitive to Sulfur Odors at Scientific American.