It’s a temporary adaptation that enables us to block out smells — good or bad — that we’re exposed to all the time, such as our deodorant or cologne.
We are surrounded by smells — dinner cooking on the stove, clean clothes tumbling in the dryer, the wet dog running through the house. Each odour consists of tiny molecules that we breathe in through our nose, where they stimulate specialised nerve cells called olfactory sensory neurons.
These neurons then send that information to our brains, where they are interpreted as specific smells. But our sense of smell has evolved to be able to dampen this response when necessary.
If olfactory sensory neurons are being stimulated by a large concentration of an odour or an odour that lingers for a long time, the neurons become saturated, says Erich P. Voigt, chief of the division of general and sleep otolaryngology at New York University Langone Health. “They’re no longer going to respond because it’s not new or necessary information, and you need to be able to smell other odorants in the environment,” he said.
While most people should be able to smell new and temporary bad breath — such as breath caused by something they ate for lunch — over time, they are likely to lose the ability to smell chronic bad breath stemming from, say, medical issues such as dental disease, infections in the sinuses or tonsils, and gastrointestinal disorders that allow odours to rise up from the stomach, Voigt explained.
When the nose is given a break from an odour, allowing the olfactory sensory neurons and brain to recalibrate, the ability to smell it should return, said Jennifer Douglas, a rhinologist and assistant professor of otorhinolaryngology and head and neck surgery at the University of Pennsylvania.
Olfactory adaptation is different from smell disorders such as hyposmia, a diminished ability to smell, and anosmia, an inability to smell at all. These disorders are often caused by illness or injury.
What else you should know
People can smell their bad breath in two ways — when the odour flows through the back of the mouth and when it flows through the tip of the nose, which people can do by blowing their breath into their hand and taking a sniff, Douglas said.
In chronic cases, once people can no longer smell their breath but have reason to believe it may be bad, Voigt suggested confiding in a family member or close friend to give an honest assessment. If bad breath is confirmed, consult a dentist or a primary care physician who can assess it and treat it or, when needed, provide a referral to a specialist.
Read More: Bad breath: What causes halitosis and do you have it?
The conclusion
In most cases, people should be able to smell new and temporary bad breath, but they will probably lose the ability to smell bad breath that becomes a chronic problem.
