Using candles for soft, ambient light and to decorate the house is popular at Christmastime, but burning them could harm your indoor air quality unless you buy the right kind. Even in the wake of new research and awareness, many people don’t realize that certain candles can increase the air pollution inside your house.

All candles release small amounts of smoke, even the "all natural" varieties. One of the problems, though, is that scented candles usually contain synthetic fragrances, and those synthetics are believed to throw more soot and possibly toxins like benzene into the air. Research is still inconclusive about whether burning scented candles can harm your health, but some studies suggest an impact.

Another concern with candles is that many of them are paraffin-based, and paraffin is a petroleum byproduct. Here again, the research is inconclusive, with no definitive proof that paraffin candles worsen air quality more than beeswax or soy-based ones. However, more and more environmentally conscious consumers are uneasy with the idea of burning a petroleum product in their homes.

Plus, some candles contain lead wicks, and guess what? Burning candles release that lead into the air, and everyone in your house breathes it in. Candlemakers in the U.S. cannot use lead in their wicks anymore, but not all countries have those same restrictions, making it imperative that you always read the labels before buying candles.

The best way to enjoy the beautiful glow of candles is to buy pure beeswax ones or those made from other natural sources with as few additives as possible. Unscented candles are cleaner than scented ones, and always buy candles with cotton instead of lead wicks.