In 2012, Chris Kelly caught a cold, which then moved into her sinuses. It was a run-of-the-mill nuisance, until she woke up one morning and realized her condition had become something far more serious.

"I opened my eyes, I went into the bathroom, I uncapped the toothpaste, and was immediately aware that I couldn't smell anything," says Kelly, who was born in Maine and now lives in the United Kingdom.

This wasn't a stuffy nose. This was like the on/off switch had been flipped.

"I was bewildered at first. I found living without smell, in the beginning, it took me a while to understand what that meant," she says.

Anosmia, the medical term for losing the ability to smell, is often referred to as an invisible disability. Colds and other viruses are a common cause, but it can also be brought on by a brain injury, or from nasal polyps. Aging is another factor. Receptors or the nerve in the olfactory system, or a combination of both, simply stop working.

And as quickly as it's lost, some anosmics will spontaneously recover their ability to smell. But not Chris Kelly. She sought medical treatment, including the limited array of options available, such as steroids and antibiotics, all to no avail.

After six months of living with the condition, she felt her well-being sharply decline.

"The most poignant loss for me was the loss of the smell of my children. And you know, my children are grown now, but when I put my arms around them, I still could easily recognize their smell," she says.

It was like every facet of her life lost a dimension. Today, though, much of her ability to smell is restored.

Retraining the brain

Kelly, straight-backed and tall, has come to the Monell Chemical Senses Center in Philadelphia to teach, and encourage, an audience of anosmics how to smell train, the tool she used to regain her sense. She's an evangelist for this low-tech anosmia treatment.

"It started out a chore, like flossing my teeth, and it has ended as a kind of altered awareness," she tells the crowd.

The smell training concept is simple: even if you can't smell anything, anosmics need to keep trying, and do so in a mindful way. Spend a few minutes in the morning, again in the evening, sniffing deeply. The repeated exposure and concentration may eventually yields results.

But don't expect overnight success. It can take months, even longer, of sustained effort.

"I'm not getting anything out of lavender, at all. Could you smell lavender?" Mary Beth James asks a fellow attendee. "Nope. Lavender is a 'no.' I'm not getting that one."

James lost her ability to smell after being hit by a car. She's here at the workshop because it's been four years, with very few gains made.

"I want to be able to smell the turkey on Thanksgiving, and the bread that I bake, and the Christmas tree. So, I'm giving it a shot," she says. "Why not?"

Scattered in front of James on a folding table are vials of essential oils, potent little jars of concentrated lavender, as well as rose, eucalyptus, lemon and clove.

There are no hard rules for what scents you should smell train with, but those are the oils recommended by Thomas Hummel, a German ear, nose and throat doctor, and a guru of modern smell training. He's published studies showing the method can work, especially for anosmics who start soon after the injury.

That hope has Kenneth Lee digging his nose deep into the rose, dreaming of just a whiff.

"You go to garden...I like gardening. But you don't smell any flowers, so..." his voice trailing off, resigned to being the saddest gardner in the world.

Since flavor and smell are so closely linked, Lee has also lost the pleasure of eating. For many anosmics, everything tastes rubbery and beige.

"You know, smell affects so much of what we experience, it is such a potent sense. It informs our sense of flavor, it really adds so much joy to life," says Edmund Pribitkin, a physician and professor of otolaryngology (commonly called 'ear, nose and throat') at Sidney Kimmel Medical College at Thomas Jefferson University. "And to lose it is really difficult. Folks become depressed, folks have all kinds of problems."

Earlier in his career, Pribitkin says he was often frustrated when he ran out of treatment options for patients. Now, he sees smell training as a way to offer, at the very least, hope.

Exactly how smell training can refresh the sense of smell isn't totally understood, but as Chris Kelly works the room, she tells people to treat it like they would physical therapy after an injury or stroke.

"You just need to persevere, she says. "There's no more magic in it than that."