Maybe you've seen something about it on the Internet, or a friend of a friend swears by it -- but you're not sure exactly what it is. Oil pulling is a growing trend, but it's not new.

"This oral therapy is a type of Ayurvedic medicine [a traditional Indian system] that dates back 3,000 years," says Jessica T. Emery, DMD, owner of Sugar Fix Dental Loft in Chicago. "It involves swishing approximately 1 tablespoon of oil -- typically coconut, sesame, or sunflower oil -- in your mouth for about 20 minutes and then spitting it out."

Unlike some so-called natural home remedies, it's not a practice that's based on pseudo-science. Recent studies show that oil pulling helps against gingivitis, plaque, and microorganisms that cause bad breath. How? "Most microorganisms inhabiting the mouth consist of a single cell," Emery says. "Cells are covered with a lipid, or fatty, membrane, which is the cell's skin. When these cells come into contact with oil, a fat, they naturally adhere to each other."