Frankincense has a long history as an ingredient in incense and perfumes, with references dating back to ancient Egypt. In the Bible, the Magi brought the fragrant resin as a gift to the baby Jesus, along with gold and myrrh — and it remains part of the classic Christmas story. But frankincense, whose smell is sometimes described as sweet or spicy with a mix of lemon and pine, will soon become only a relic of the past if nothing is done to protect the trees that produce it, according to a new study.