The weird connection between pain and smell - and how people lose both

It's been known for some time that certain people are physically unable to feel pain. A new test shows that those people are also unable to smell any scents.

The SCN9A gene is the helpful little guy that tells people when they sit on a tack, or when the water in the bathtub is too hot, or when they've strained their backs. It controls nociception - the nerve response that allows people to feel pain. When it mutates, the body can still feel most sensations, but it doesn't feel when those sensations cross the line into pain. Although it may seem like a blessing, pain is a very useful alert system for the body. People with mutated SCN9A can do a great deal of damage to their bodies before they realize they have to seek medical help. Often it's only after some serious injury or medical problem that people realize that they have the disorder.

The disorder was thought to stand on its own, without further complications from the pesky gene. A recent study shows that there is more to this mutation than previously thought. Researchers rounded up people with SCN9A mutations - generally discovered after the people broke bones without feeling pain, but sometimes found after they'd given birth painlessly. They put them in a room and played a simple game; Stinky-Stuff or Water. People with SCN9A mutations were unable to distinguish balsamic vinegar from water. They were unable to distinguish orange or mint smell from water. They were even unable to distinguish perfume from water when the perfume was so concentrated that other people in the room could barely stand to stay. The study indicated (overpoweringly sometimes) that those who feel no pain are also anosmic.

What's strange is that, not only had the subjects often not noticed the lack of scent, nobody else had either. Although congenital insensitivity to pain has been a subject of curiosity for the public and the medical community, nobody thought to check the patients noses (unless they were bleeding). Since everyone thinks that the way they experience the world has to be normal, the anosmia remained undetected. So, the next time you're in a lot of pain, try to go out and smell something nice. Not everyone is as lucky as you are.

Via Science News and Nature.