Indoor air quality experts in US have said that scented candles and air fresheners which make our homes smell nice, could contain hundreds of chemicals that are harmful to us.
According to experts at the Oregon Environmental Council, some of those chemicals could have a wide-range of health effects.
An example is Portland resident Ashley Henry, who developed asthma last spring, and became hypersensitive to fragrances and other chemicals in her home.
"I was a big fan of scented candles, but I had to eliminate use of those," KATU quoted her as saying.
"It was a burning sensation," she said.
According to Jen Coleman at the Oregon Environmental Council, so-called "indoor air pollution" can cause a range of problems.
"Sometimes it can just be a matter of a little bit of a cough and itchy eyes and you don't know why. That can be an air quality problem," Coleman said.
If smells linger in your house, Coleman recommends you avoid masking the smells with fragrance. Instead, try to increase circulation in your home.
Many candles and scented products also contain chemicals that companies aren't required to disclose on the label, and some labels simply list "fragrance" as an ingredient without giving any specifics.
Coleman said there can be hundreds of chemicals that go into scented candles that consumers don't know about.
She said some contain chemicals called "phthalates", which helps smells linger.
The Environmental Protection Agency reported there is evidence that phthalates cause birth defects and reproductive problems.