While incense is often linked to meditation and tranquility, it's now being linked to something much, much different -- cancer of the upper respiratory tract.

To clarify, only use over long periods of time appears to increase the risk, and it does not increase the overall risk of lung cancer. A study found that "Incense burning almost doubled the risk of developing squamous cell upper respiratory tract carcinomas including nasal/sinus, tongue, mouth and laryngeal. There was an increased risk both in smokers and in nonsmokers, pointing to an independent effect of incense smoke."

As scary as this sounds, as long as you're not filling your room with incense every day, year after year, you're probably in the clear. However, it's good to be aware that burning incense or candles introduces environmental pollutants into your home, which isn't the best thing in the world for your health. If you yearn to burn, do your homework first!

Source