Sensitivity to smells explained

Oct 31 2007

Some people are oblivious to the odor in the locker room after a game, while others wrinkle their noses at the slightest whiff of sweat.

Research by Prof. Doron Lancet, research student Idan Menashe, and colleagues, published in this month's PLoS Biology, shows that this difference is at least partly genetic.

Our sense of smell often takes a back seat to our other senses, but humans can perceive up to 10,000 different odors. Like mice, which boast a highly developed sense of smell, we have about 1000 different genes for the smell-detecting receptors in our olfactory “retinas.” In humans, however, over half of these genes have become defunct in the last few million years. Some of these genes are “broken” in all people, while others still function in some of the population.

Lancet and his coauthors, from several institutions in Israel and Florida, had their experimental volunteers sniff varying concentrations of compounds that smelled like banana, eucalyptus, spearmint, or sweat. They compared their ability to detect each odor with their patterns of receptor gene loss. The team found that one gene (OR11H7P) appeared to be associated with the capacity of smelling sweat. When participants had two genes with disrupting mutations, they were likely to be impervious to the offending odor, while those that were hypersensitive to the smell had at least one intact gene.

The scientists noted, however, that while having at least one intact OR11H7P gene might determine if you can smell whether your loved one has just come from the gym, this is not the entire story. Women were generally slightly more sensitive to many smells than men, and some individuals of both sexes were better or worse in across-the-board acuity to all odorants. Furthermore, as is always the case, not all variation was caused by genetic differences; environmental factors were seen to play an important role as well.