A Canadian study that explored alternative medicine therapies for allergies and asthma concluded that “many of the testing methods and treatments advertised on alternative medicine websites do not have any research evidence to support them, and only two treatments mentioned are proven to work.”

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

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

“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.

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