A small number of laboratory studies have suggested that frankincense oil may contain some properties that affect cancer cells, but there is no evidence yet that it can treat or prevent cancer in humans. Of a handful of in vitro studies (involving cancer cells in a petri dish) and a study with mice, some have reported that the frankincense extract or oil they tested stopped cancer cells from growing or caused apoptosis (cancer cell suicide). However, the bioactive compound and how it works on cancer cells are not clear. What has been tested is not the frankincense essential oil you buy from a health food store, but the plant resin or gum produced by the boswellia tree, which has been used in traditional medicine in many African and Arabian countries with reported anti-inflammatory and immunity-boosting properties. Studies to date have used extracts or oil from the gum of different species of boswellia (gum resins are different depending on the geographical conditions where the tree is grown), in different concentrations and with different types of cancer cells (including bladder, breast, bowel, liver, ovarian and pancreas). Much more research, including clinical studies in humans, is necessary to work out if frankincense oil can be used as a cancer therapy in humans.