I actually met a friend of mines recently and unfortunately due to a head injury lost his ability of smell. The doctor’s didn’t realize it and neither did he for quite while till one day he got sick eating fish from his refrigerator that was stale and he couldn’t figure out. So, it definitely plays an important role. On the positive side he doesn't detect any bad odors, but that means he wouldn’t know he is stinking either. He makes sure he is well cologned/deodorant-ized :) Also, he misses the smell of delicious food and other good things!