History:  Frankincense is a leafy tree that grows without soil along the rocky shores of Somalia.  The medicinal part of the tree is the resinous gum obtained when the bark is cut into.  This resin, which is collected and allowed to harden in the open air for several weeks, is also used in traditional incense the world over.  Other species include B. serrata.

Cautions:  Mild skin irritant.  The oil should be diluted with a carrier oil, such as jojoba or sweet almond.