Dogs have more types of olfactory receptor than we do – but as Mainland points out, cows have more than dogs (about 1,200 compared with 800) and it’s not clear that cows are significantly better at smelling. The poor reputation of humans may be down to the fact that we spend comparatively little time actively sniffing and so training our sense. What difference would it make if we all put more effort into smelling the world around us?

Emotional state

One reason to enhance our sense of smell would be to help us better navigate our social world. Some people born without being able to smell may have trouble identifying the emotional states of others, says Mainland. They’re aware that while they rely heavily on facial expressions, for example, friends who can smell somehow seem to be picking up on signals they’re missing, signals that are so powerful they can override the emotional information contained in a smile or a frown.

They’ll talk about meeting up with a group of friends, Mainland explains, and one friend might say of another: “Oh, she wasn’t happy at all.” And they’ll say, “She looked happy.” And the other will say, “Yeah, she looked happy, but she clearly was not happy.”

Researchers have also found that smell can change your mood and behaviour. George Preti at Monell and colleagues have found that extracts of male underarm odours can not only influence female physiology, altering levels of a hormone involved in regulating the menstrual cycle, but also make women feel more relaxed and less tense. And along with Pam Dolton, he has also found evidence that people can detect “stressed” body odours, often without realising.

Read more about how smell influences how we perceive the emotional state of other people.



So, those with no smell may be missing out on many subtle social signals. Can anything be done for them? There are some effective treatments. If the loss is due to chronic sinus disease, you can treat that condition and reverse the smell loss – sometimes very rapidly. But for patients like Johnson, there’s very little that can be done. He came to Monell to ask the researchers here if they had any advice, and the main recommendation was to actively smell a few different things a couple of times a day, because there’s evidence this can help to stimulate the system and may aid recovery.