Max Livesey was on holiday when he suddenly noticed the smell of burning leaves. He glanced around his hotel room but saw nothing that could have caused the strange aroma. Over the next few weeks, the smell intensified, ranging from burnt wood to an oniony-gas. Eventually, he was convinced there was a family of skunks around. “My eyes started to water, and I had this strange sensation in my throat that I couldn’t get away from,” he says.

Livesey (not his real name), now a 72-year-old software engineer, blamed the weird smell on the musty hotel room. But the phantom smells returned when he was back home, increasing throughout the day and persisting for hours.

Livesey went to see Alan Hirsch at the Smell and Taste Treatment and Research Foundation in Chicago, who specialises in smell disorders. Hirsch tested his general olfaction by getting him to smell different odours at a range of intensities. He discovered that Livesy’s ability to sense ordinary smells had been impaired. This was not entirely unexpected: Livesey had Parkinson’s disease, and a poor sense of smell is a common symptom. This is likely due to the disease causing damage to the olfactory nerves, which are cells that transmit information about sense of smell from the nose to the brain.

The human barometer

But why the hallucinations? Occasionally, we all get what’s known as “spontaneous olfactory discharge” where our olfactory nerves become briefly active. Normally, this discharge is inhibited by other neurons sending out information about real smells, and so it doesn’t amount to anything. However, an impaired ability to smell stops these olfactory discharges from being suppressed, which means they are consequently perceived as phantom odours. (For a similar reason, some people with hearing difficulties can start to notice haunting strains of music that are purely the product of their mind.)

“My eyes started to water, and I had this strange sensation in my throat that I couldn’t get away from”

However, Livesey had started to notice something even more peculiar: his hallucinations would get worse just before a storm. Two to three hours before clouds gather, his phantosmia intensifies and persist throughout a storm. Sometimes, he says, he can predict a storm coming up to ten hours before it starts.

Hirsch says this is the first case of weather-induced phantosmia he has ever come across. It’s not, however, the first time that weather and human ailments have been linked.

My knees hurt... it must be about to rain

Over two thousand years ago, Hippocrates observed a link between neurological complaints and the weather. In 1887, researchers first investigated this relationship and found a significant link between temperature and humidity and the intensity of joint and muscle aches in people with chronic pain. Since then, links between the weather and migraines, as well as the weather and pain in people with multiple sclerosis have been well documented.

Less well-known is the fact that our sense of smell is also known to decrease with a drop in air pressure, says Hirsch. Since a drop in barometric pressure that precedes a thunderstorm would reduce Livesey’s olfactory ability even further, it may serve to further increase his phantosmia.

Of course, Livesey’s phantom smells may simply be a case of recall bias, where a selective memory may lead him to notice the times that his phantosmia gets worse before a storm than when it fluctuates at other times. Or it could be that he’s already been primed by a weather forecast beforehand. Livesey doesn’t believe this is the case – on many occasions he has not seen a forecast, yet was still able to predict the onset of bad weather.

Hirsch also believes that a real link between weather and phantosmia exists. He says that you also see phantosmia when you put someone – say a mountaineer training for a high altitude environment – into a hypobaric chamber, where they experience low ambient air pressures. “We also see phantosmia in people who are on long excursions in high altitude areas of Antarctica,” he says.

Since meeting Livesey, Hirsch has treated a few other individuals with similar complaints: “Everyone we’ve seen so far has a somewhat impaired sense of smell in normal conditions and describes how the hallucinations are most intense right before a storm,” he says.

Going up?

It’s a difficult problem to investigate objectively. In one preliminary experiment, Hirsch tried to induce the hallucinations by getting his patients to travel in the express elevator up to the top of the John Hancock Centre – a 100-story, 1,127-foot tall skyscraper in Chicago. Although it had little effect on Livesey’s phatosmia, Hirsch says that the resulting change in pressure did increase the intensity of some of his patient’s phantom smells, which suggests that the problem may well be sensitive to subtle changes in air pressure.

When they’re at their most intense they can smell like excrement

Unfortunately, there’s no permanent treatment. A few years ago, Livesey added L-dopa to his drug regime for Parkinson’s, and for a couple of months his hallucinations were barely noticeable. Recently, though, they’ve had some bad weather in Chicago and his phantosmia has returned.

One idea was that he might be able to reduce the hallucinations by boosting his remaining sense of smell. A few months ago, on Hirsch’s recommendation, he started sniffing three different scents, three times a day – these fragrant scents appear to replace the hallucinated smell. “It seems to be helping,” he says, “but maybe that’s just wishful thinking.” Mostly, he just tries to ignore the smells. Focusing on work helps, he says, as does laughing and eating.

Livesey’s hallucinations aren’t painful but they are annoying, he says. “When they’re at their most intense they can smell like excrement – that’s rather distracting.”

The smell sometimes changes but he says it’s almost always unpleasant. “There are also the physiological effects that I get from the smell, like watery eyes,” he says. “I read about some people who hallucinate the smell of roses. I’d like to know who that is – I’d prefer that!”

I wondered whether anyone ever asks him what the weather’s going to be. He laughs. “No, it’s not 100% accurate. I’m not the national weather service. If they do, I tell them to go look at their iPad!”

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