Key Takeaways for What Is Nose Blindness?
- Olfactory adaptation, or nose blindness, is the result of your nose becoming "blind" to certain odors or smells.
- Your nose does this as a way to help your brain focus on new or potentially important smells that may arise, such as burning.
- If you're worried that your home may smell, ask a friend or family member to take a sniff. Leaving your home for over 2 weeks can also help you rest your nose and overcome nose blindness.
Very high up in your nose, there’s a small patch of tissue called the olfactory epithelium that’s loaded with olfactory receptors. These receptors detect odors and send messages to your brain, which interprets those messages as the variety of smells that make up your world: freshly baked sourdough, honeysuckle blossoms, a waft of incense smoke, or maybe, dog poop.
But those smells, whether as lovely as bread or as off-putting as dog poop, can be quite short-lived. For many odors, the perception of smell starts to diminish after just one or two sniffs, Pamela Dalton told Discover. Dalton is a researcher at the Monell Chemical Senses Center, a non-profit that does basic research on the senses of taste and smell.
The phenomenon is called olfactory fatigue, or more colorfully, nose blindness.
Read More: There's a Reason Why Smelly Feet Are So Hard to Ignore — Here's What You Can Do About It
What Causes Nose Blindness?
After a time, you can become oblivious to the smells around you. The brain does this all the time with sensory input. Take sound, for example. Imagine there’s noisy construction work going on outside, Dalton said. For the first few days, the racket drives you up the wall. But after a while it seems to recede into the background, and you hardly notice it anymore.
Explore All OptionsThat’s what Dalton calls “a central filtering phenomenon.” Nothing has changed with your ears; they haven’t lost any sensitivity, Dalton said. You’re just not paying attention to the noise anymore.
But with smell, something different is going on. With nose blindness, the receptors actually stop responding to the smell.
“They enter into a refractory period when they just can’t fire again, and there won’t be any signal going up to the brain,” Dalton explained.
Why Do We Become Habituated to Smell?
Researchers believe the reason we become habituated to smell (as well as to other sensory input) is that if we didn’t, our brains would become overloaded and potentially miss some important information. The brain has to keep channels open in case a really important smell — leaking gas, burning paper — comes along.
Nose blindness is not permanent, but it can be persistent, Dalton said. In one classic experiment, published in Perception & Psychophysics, she and her colleagues placed a scent composed of a single compound into a small dispenser. Subjects placed it by their beds at night for two weeks. When tested in the laboratory over the course of two weeks, they required two, three, and sometimes even four times the original amount of the compound to detect it.
“They would almost have to go right up to it and put their nose over it to get enough of a burst to overcome that adaptation,” Dalton said.
But here’s the really interesting part: After the researchers removed the diffusers, it took a full two weeks, in some cases even a bit longer, before participants could again detect the smell.
The More You Worry, The Less Likely You Are To Adapt To It
The effect is not the same for all odorants, though. In a 2017 paper published in the journal Nature Scientific Reports, researchers found a lot of variation in how much and how quickly odorants induced nose blindness. They also found that the more unpleasant the odor, the less people became habituated to it, though the paper’s authors noted that other studies have found that when it comes to really stinky smells (malodors), people adapted more quickly. (None of the samples in the 2017 study were super stinky.)
Here’s another intriguing fact: The more you’re worried about a smell, the less likely you are to adapt to it. Dalton described one study in which she and her colleagues exposed people to an odor for 20 minutes, which was plenty of time for them to adapt to the smell.
However, before exposing them to the odor, the team told the participants that the smell was known to cause problems with health and cognitive function. When participants were told this, they were less likely to adapt to the smell.
For a lot of people, the takeaway from this is: “Oh no! My house might stink, and I don’t know it!” According to Dalton, there are only two ways to know for sure if your house stinks. Go away for two weeks. When you come back, you should be able to detect what your house smells like.
If you can’t manage a two-week vacation, ask a friend or neighbor to come over and give your digs the sniff test. Just be sure to choose someone who will break the news gently if it turns out your house has an odor problem.
Read More: First-Ever Smell Map Is a Breakthrough in Sensory Research, a Step to Help Us Tackle Loss of Smell
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Nature Scientific Reports:New determinants of olfactory habituation
- This article references information from a study published in Perception & Psychophysics: The nature and duration of adaptation following long-term odor exposure
- This article references information from a study published in Chemical Senses: Odor Perception and Beliefs about RiskNose
