You smile to yourself, as you hang the mistletoe in a prominent doorway or from the bottom of a chandelier, every holiday season. You think about all the times you were kissed under it-or all the times you wanted to be kissed, but weren't. And this year, just as it crosses your mind that you have no idea why this strange plant became a Christmas tradition, your child watches you and asks: "What is that?" "Mistletoe", you answer, hoping that will satisfy him. It doesn't: "It's a toe?" "No", you reply, realizing that your parental omniscience is about to be challenged, "It's a plant." "Why are you hanging it up?" "So Mommy and Daddy can kiss underneath it." He looks at you like you're speaking Greek. You know the next word: "Why?" "Because", and you know how lame you sound, "that's what people do." "Why?"

This could go on for hours, because, in fact, you don't know the answer, do you? You hang your mistletoe every year when you decorate (hopefully, it's plastic, since the real thing yields toxic berries), but you don't really know where the tradition came from.

Well, no one knows, exactly, but mistletoe-a parasitic plant found on trees, the seeds of which are spread by birds and wind-has been an object of mystery in many cultures, dating back thousands of years.

Based on their mythology, the Vikings believed that mistletoe had the power to raise the dead. They believed that Balder, the son of their goddess of love and beauty, Frigga, was killed by an arrow tipped with the poison in mistletoe. Frigga mourned so deeply that her tears turned the red berries of the mistletoe white, and Balder was revived. Frigga was so grateful that she reversed mistletoe's previously deadly reputation, and henceforth she kissed everyone who walked underneath the plant.

The Druids of ancient Britain believed that mistletoe had miraculous properties, that it could cure disease and provide fertility in humans, and that it would protect against witchcraft.

In fact, today, mistletoe extracts are being tested for use in some forms of cancer chemotherapy-it's been shown to kill certain cancer cells in the laboratory-as well as to mitigate the negative effects of other chemotherapies, and to boost the immune system. In Europe and Asia, mistletoe extracts are used to treat all kinds of ailments, like arthritis, rheumatism, hypertension, epilepsy, and menopausal symptoms.

None of this will answer your five-year-old's question, about why you hang it in your home, today, and why you kiss Daddy everytime you're both underneath it. So just tell him, we hang mistletoe today to remind us of the need to show our loved ones how we feel about them. Then pull him over, under the mistletoe, give him a big hug and a kiss and tell him how much you love him. It won't matter to either of you why we do it, every year-but it will feel like a great tradition to keep.