Despite decades of progress on the management of asthma, millions of sufferers still have symptoms, leaving many looking for alternative ways to help their condition.

A small, but apparently increasing number of people are turning to a little-known method: breathing in a fine salt mist in man-made salt caves.

Salt therapy, also called halotherapy, is based on a theory developed about 100 years ago by a Polish physician who noticed that people who worked in salt mines had fewer respiratory problems. While it's not clear how the therapy might work, it's thought that the salt has antimicrobial properties and helps to relieve mucous build-up.

Now, a number of facilities are cropping up that promise to recreate the environment of real salt mines.

Margo McIntosh, 57, is one of those who uses salt therapy. Once a week, she steps inside the Iris Salt Rooms in Waterloo, Ont., where the walls are stuccoed with the stuff and where a fine mist of salt is pumped into the air. The spa uses something called a halogenerator, which crushes rock salt into micron-sized particles that can travel deep into the lungs.

McIntosh says visiting the salt cave regularly is helping control her asthma better than any medication ever did.

"It's been really great. I've just had my ninth treatment just before we were talking and I've got my asthma inhaler down to one puff a day with no coughing, no symptoms," she tells CTV News.

Olga Fediounin takes her five-year-old son Nikita to the Iris Salt Rooms as well, after he developed problems breathing at night.

"He's always had a stuffed nose that he couldn't breathe through. He had to use the nose sprays and all kinds of things," says his mother.

She began by taking him for daily sessions for 12 days, but now comes just once a week. Her kindergartener plays in piles of salt on the floor with an assortment of toys, seemingly unaware that all that play might be therapeutic.

"It's working very well for him. He breathes better during the night," says his mother. "He doesn't breathe heavy anymore, he breathes through the nose and before I noticed that he wouldn't breathe full enough at all."

Olga says she's not deterred by the fact that there's not much solid scientific evidence backing up the use of salt therapy for respiratory conditions. She had heard anecdotal reports from people who said they simply felt better after trying the therapy, so she decided it was worth a try.

"I think everybody has a choice, you come and try it yourself because if nothing scientific will be proven, it doesn't mean that it doesn't work," she says.

Richard Zagrobelny not only runs the Iris Salt Rooms in Waterloo, he helps people construct their own caves. He says there are more than a dozen salt rooms across Canada, with more being planned.

"Every time I build a salt room, immediately I get many, many more inquiries from that place," he says.

Toronto-based asthma specialist Dr. Mark Greenwald, who's also the vice president of the Asthma Society of Canada, says he's doubtful of the health benefits of salt.

"It's nice, but it has no therapeutic benefit other than putting it on their french fries to make them taste better," he says.

He says patients should focus on their medications, and getting rid of dust mites and allergy-aggravating pets in their homes over an unproven method like salt therapy.

"We do not have any scientific information that says there is a true medical benefit," he says.

But asthma sufferer Rosa says scientists should consider studying the therapy so that they can see that it works. She says she used to have trouble even going from her front door to her car. Now, after trying salt therapy, she's much better.

"My puffer use is down and I can walk a block or two blocks. I couldn't before, because I would take five to eight steps and heave, just trying to get your breath. Now I can walk, I can go up stairs," she says.

Zagrobelny says he has approached some asthma researchers to offer to help scientists collect some data based on the patient experience.

"I would invite anybody who's willing. My doors are open any time and I would help in whatever is needed to finally have North American study done on the subject," he says.

With a report from CTV medical specialist Avis Favaro