The most common cause is a viral infection or sinusitis. Rare causes are tumours or cancerous growths in the nose or severe trauma to the head, such as being involved in a high- impact car accident.
Joy always believed her olfactory nerves were severed by the oxygen mask she wore in the incubator after her premature birth. She has a scar in the middle of her forehead to remind her of it.
However, ear, nose and throat surgeon Dr John Steer believes
Joy must have been born this way.
"The skull is extremely protective of the olfactory nerves and it would have taken a severe head trauma for the brain to shear off the nerves."
But Dr Steer also says, "Rarely is one born without a sense of smell. Anosmia is almost always a symptom that is acquired."
The olfactory sense is situated in one of the most primal parts of the brain, above the nasal passage. This region, the nasal mucosa, contains about 10 million receptor cells. Smells travel in the form of airborne molecules to these receptors, where it affects our thoughts, emotions and behaviour.
Although humans have a less acute sense of smell than most animals do, we can still detect between 2 000 and 4 000 unique smells, sometimes up to 10 000. If these nerves are damaged, the person will experience complete or partial anosmia. In the rare case that the nerves never formed, as probably happened in Joy's case, it is called congenital anosmia.
"In Grade One," Joy says, "I remember the other kids going on about smelling Chappies. I thought I was a little slow and wasn't doing it properly, because I wasn't really sure what they were talking about."
Joy didn't confront her parents until high school and meanwhile pretended to other kids that she could smell by taking cues from them. "The first thing my parents said was, 'It's impossible – if you can taste you can definitely smell.' Their disbelief made me start to doubt myself. I thought maybe it was psycho somatic and that I could smell but didn't know it."
What it means
Dr Steer says the role of the nose is underplayed, even in medicine. "Nasal dysfunction has an enormous impact on the quality of a person's life. All too often people say, 'It's just a blocked nose; next please.'"
He says in losing the ability to smell, we lose one of our most basic warning signals. In more primitive times, a person needed smell in order to detect danger. "If your nose was blocked you would lose an important part of the body's defence mechanism. Your body would become fatigued to force you to stay in the cave away from danger.
"In the modern world, our sense of smell still warns us of ominous environments but, more importantly, it contributes to how we recognise one another, using our pheromones – airborne hormones linked to our olfactory sense. It's the most honest way we have of judging whether we like someone." Joy says she assesses her world according to visual and auditory stimuli. "I walk into a room and make my judgements by what I see. People say you make a good match with a guy with the right smell for you, so I could make a big mistake. Apparently guys smell either like coffee or mothballs."
How does it happen?
Most people develop anosmia after having lived with a functioning olfactory sense. Losing it can be traumatic. It can mean a huge adjustment on a practical, emotional and intimate level.
Semwano Chonya, a 27-year-old Tanzanian, has been living in Cape Town for the past seven years and works as a hotel manager. A year ago she was mugged and pushed off a moving train. She woke up in hospital after being on a life-support machine for a week with severe migraines from the head injuries she had sustained.
Semwano says her sense of smell was totally gone for the first two months after the accident. "But then it started to come back and I had hope. My neurologist said if it came back it would start with one smell for everything... and it would be the smell of burning tyres."
In her case, certain things all smelled the same – like coffee, bacon, garlic and even smelly feet. "That one gross smell used to make me want to gag," she says. "These days I think I have only one smell for good and one for bad."
Through counselling she is learning to adapt to the radical change. "It has affected every area of my life. I haven't fully accepted that one of my five senses is gone."
Can you taste?
A neurologist based at Groote Schuur Hospital, who asked not to be named, says when the skull is under severe stress, those nerves can get severed.
"They can't regrow, but the person can still taste because the taste buds are a different mechanism."
Joy agrees that not being able to smell does not necessarily mean you can't taste.
"I really love food, although I'm totally disinterested in cooking and I think it's largely because I can't smell. I imagine what food smells like by how it looks or tastes. I have a sixth sense about it." She is drawn to pungent tastes and things that have a distinct flavour, such as blue cheese.
"In essence, people who can't smell can't taste well and go more on the texture of foods rather than on actual taste," says Dr Steer.
But Semwano insists that she has slowly begun to gain some control over her taste buds and to differentiate between sweet, sour, bitter and salty.
"Somewhere in my brain there is a memory of how things are supposed to taste and smell, and every day I tell myself it will taste like it should."
As for evocative, pleasurable aromas, Semwano most misses the smell of perfume.
"I used to have a passion for perfume, but now I have to stick to what I know works for me,"she says.
No turning back
Dr Steer says it is highly unlikely for one's sense of smell to return after suffering a head trauma. He advises patients, especially those who lost their smell as a result of a viral infection or sinusitis, to wait two years before making the final analysis and in the meantime to consult a specialist.
But there are exceptions to this rule, if inexplicable ones.
"I treated a woman who had been stabbed in the head and lost her sense of smell completely," says Dr Steer. "Later she told me her sense of smell came back after she'd tripped over a table."
Sometimes anosmia can be a blessing – think stinky public toilets, manure, exhaust fumes and rubbish dumps. While the rest of us are gagging and holding our noses, the Joys and Semwanos of this world are blissfully unaffected.
"I could be with a great guy even if he stank or I could happily pack fish in Alaska one day," Joy says.
"Maintaining a sense of humour and surrounding yourself with loving people makes all the difference," Semwano says. "It really helps to have an understanding doctor and a mother who reminds you of your blessings."