Smelling disorders, including phantom smells and a lack of smell, can be a sign of serious health problems.

In a 2009 episode of “Mad Men,” a character with some major health issues — stroke and dementia — mysteriously smelled oranges while eating chocolate ice cream. Shortly after, the man dies while standing in line at the A&P.

Was the phantom orange scent a warning sign of his impending doom?

It’s possible, says Dr. Alan Hirsch of the Smell & Taste Treatment and Research Foundation in Chicago.

“By all means, a phantom smell could mean something serious,” says the psychiatrist and nationally recognized smell and taste expert. “It absolutely needs to be evaluated. It could be a tumor – that’s on the top of your list of things to rule out — but it could also be a cyst or some infectious agent housed in the area of the brain where the smell is processed.”

Brief episodes of phantom smells or phantosmia — smelling something that’s not there — can be triggered by temporal lobe seizures, epilepsy, or head trauma. Phantosmia is also associated with Alzheimer’s and occasionally with the onset of a migraine.

But it’s not typically something sweet that’s conjured up by the brain.

“It’s usually more unpleasant stuff or odors that are hard to describe,” says Hirsch. “People will say it’s chemical-like or talk about a burning smell.”

Common olfactory hallucinations include lots of icky odors. Sufferers report smelling hydrogen sulfide (rotten eggs), bad perfume, garbage, a gas leak, wet dog, pungent body odor or spoiled fish or feces. The brain may trigger such sickening odors instead of agreeable ones because humans learned very early to avoid noxious smells for survival.

“I think a larger area of the brain is represented by bad smells than good smells,” says Hirsch. “And they also may be easier to ‘fire off.’”

Smell disorders aren’t that rare. According to a 1994 survey, 2.7 million Americans have some type of olfactory problem, including anosmia (the inability to smell); hyposmia (a decreased ability to smell); parosmia (a distorted perception, instead of flowers, you smell rotten meat), and phantosmia. Another 1.1 million people have issues with taste (smell and taste are inextricably linked) including ageusia (the inability to taste); hypogeusia (a decreased ability to taste) and dysgeusia (a distorted ability to taste).

Phantom fragrances can be produced by one or both nostrils and can waft in and out of a person’s life over the course of a few hours or a few days or a few weeks. In some cases, such as that of a 35-year-old New Zealand woman who said her nose caused everything to “smell blimmin’ awful” for 17 years, the condition can come and go for no apparent reason for decades.

In a New York Times story, a woman suffered a succession of unpleasant phantom odors, from dank earth to burnt chili. When antibiotics failed to treat the condition, she simply learned to live with it — and avoid disagreeable odors.

Even if there is no underlying tumor, epilepsy or some other infection, problems with your sense of smell can be very disabling.

“Frequently, [patients will] lose a substantial amount of weight because they can’t stand the way everything tastes,” says Hirsch.

Furthermore, doctors will often treat it like a psychiatric problem, with patients visiting an average of seven physicians before getting help, says Hirsch. The irony is, some people with phantosmia will develop psychiatric disorders, depression or suicidal behavior as a result of their condition.

“Approximately half of my patients who have sought surgery for their distortions have at one time considered suicide because of the hopelessness of living a life where all food smelled like spoiled meat or worse,” Dr. Donald Leopold of the University of Nebraska Medical Center’s otolaryngology department wrote in the 2002 edition of Chemical Senses.

Sometimes people think the stink is coming from themselves, which can lead to a condition known as olfactory reference syndrome, says Hirsch.“They’ll wash frequently and won’t go out. It will start with phantosmia, but then they’ll develop secondary paranoia as a result.”

Medical tests such as MRIs, CT scans and EEGs can find common physiological triggers such as tumor, sinus infection and epilepsy, but some patients never understand why they’re suddenly inundated by the smell of garbage or rotting fish or burned coffee or cheese. While pinpointing the cause of phantosmia can sometimes be difficult, treatment is available, including nasal saline drops, anti-depressants, sedatives and anti-epileptic drugs.

Most patients respond to medication, however, a surgical procedure involving the olfactory bulb has also been shown to provide relief. Although normal aging brings a gradual loss of smell, phantosmia sometimes occurs with a reduced ability to smell real scents, another matter that can have serious ramifications, Hirsch says.

“AIDS can initially present with smell loss,” he says. “Or it could be anything from vitamin deficiency to Alzheimer’s to hypothyroidism to head trauma to stroke to diabetes to medication to leprosy.”

One quick way to test whether your sense of smell is diminished is to dish up a bowl of ice cream.

“Take some vanilla ice cream and some chocolate ice cream and see if you can taste the difference,” says Hirsch, who says ninety percent of taste is smell. “If you can’t smell, they both taste the same.”