Health Canada is reminding people to stay away from so-called "designer drugs," including synthetic marijuana, that's being sold across the country.

The psychoactive drugs, which are being marketed as "herbal highs" or "legal highs," are illegal in Canada and can be extremely dangerous, the federal department said Friday.

Health Canada said consuming the drugs can cause, among other things, hallucinations, seizures, psychotic episodes and even death.

The department says new psychoactive substances are rapidly becoming more available in Canada.

A CBC News investigation earlier this year found that herbal incense, which can give a high similar to marijuana, was available to buy in stores from St. John's to Winnipeg to Vancouver.

Packages of the herbal incense, popularly known as "spice" or K2, contain explicit health warnings that it is not for human consumption.

However, undercover CBC reporters found stores where staff suggested the product is meant to be smoked. As well, numerous YouTube videos show people smoking the "incense."

Proponents of synthetic marijuana argue that it is legal, but Health Canada considers it a controlled substance if it gives the same effect as marijuana.