Alternative medicine practitioners like homeopaths and acupuncturists may claim to treat allergies or asthma, but a study in Canada found that many there offer remedies that are unproven or even dangerous.

"Complementary and alternative medicine continues to grow in popularity - particularly in the areas of allergy and asthma - despite ongoing controversies," said lead author Timothy Caulfield, research director of the Health Law Institute at the University of Alberta.

"Both asthma and allergies can be a serious health condition," Caulfield told Reuters Health by email. "These kind of public representations can be misleading and may lead to inappropriate care."

The researchers write in BMJ Open that government data from 2008 found that more than 70 percent of Canadians use complementary and alternative medicine.

In the U.S., they say, people spent over $30 billion on complementary and alternative medicine in 2012 alone.

More on this...

Caulfield and colleagues sought to investigate alternative medicine practitioners' marketing claims, including those of chiropractors and acupuncturists.

They also investigated claims made by homeopaths, who use diluted plant and mineral tinctures as treatments, and naturopaths, who use a combination of various alternative medicine remedies to treat illness.

The study team performed Google searches in March and April of 2016 and identified 392 websites of alternative medicine clinics located in 10 of Canada's largest cities.

The researchers checked to see if the websites mentioned allergy and food sensitivities or asthma, and if they claimed to be able to diagnose or treat the conditions.

Overall, alternative medicine websites were more likely to advertise that they could treat allergy or asthma rather than diagnose it.

More than half the sites claimed to treat allergy or asthma, while only a quarter claimed to diagnose allergy and about 3 percent claimed to diagnose asthma.

Naturopaths were most likely to make a claim about diagnosis or treatment, with 85 percent making claims about allergies and 64 percent about asthma.

A majority of acupuncturists, 68 percent, and homeopaths, 60 percent, made claims about diagnosing or treating allergies, while around half of both groups claimed to diagnose or treat asthma.

Chiropractors were the least likely to make claims about allergy or asthma, with a third of websites mentioning allergy and 38 percent mentioning asthma.

Many of the testing methods and treatments advertised on the alternative medicine websites do not have any research evidence to support them, the researchers write, and only two treatments mentioned are proven to work.

Some advertised treatments, including spinal manipulation and injection of hydrogen peroxide, may actually cause harm to patients, the researchers write.

The researchers also noted that some websites cited medical treatments like antibiotics and vaccinations as a cause of allergies and asthma.

"Allergies including asthma affect a high proportion of children and adults resulting in a high burden of disease and uncommon but preventable deaths," said David Osborn, a clinical associate professor at the University of Sydney who studies allergy treatments.

"It is unethical to advertise products that do not work or may do harm, particularly if claims of benefit are being made, which they frequently are," Osborn, who was not involved in the study, told Reuters Health by email.

Osborn added that patients often will not research whether advertised treatments actually work.

"From the medical point of view, we are highly concerned about the use of unproven and potentially harmful tests and treatments," Osborn said.

The researchers say new policies may be needed to protect the public.

"People should be very skeptical of the marketing information found on these websites," Caulfield said. "Seek out independent, science-based information!"