Frankincense is a fragrant gum resin from trees of a genus (Boswellia of the family Burseraceae) of Somalia and southern coastal Arabia that is an important incense resin and has been used in religious rites, perfumery, and embalming.
In the Bible the first mention of incense is recorded in Exodus 30. 34And the LORD said unto Moses, Take unto thee sweet spices, stacte, and onycha, and galbanum; these sweet spices with pure frankincense: of each shall there be a like weight:35And thou shalt make it a perfume, a confection after the art of the apothecary, tempered together, pure and holy:36And thou shalt beat some of it very small, and put of it before the testimony in the tabernacle of the congregation, where I will meet with thee: it shall be unto you most holy.37And as for the perfume which thou shalt make, ye shall not make to yourselves according to the composition thereof: it shall be unto thee holy for the LORD.
Resins 65 per cent, volatile oil 6 per cent, water-soluble gum 20 per cent, bassorin 6 to 8 per cent, plant residue 2 to 4 per cent; the resins are composed of boswellic acid and alibanoresin.
Medicinal Action and Uses
It is stimulant, but seldom used now internally, though formerly was in great repute. Pliny mentions it as an antidote to hemlock. Avicenna (tenth century) recommends it for tumours, ulcers, vomiting, dysentery and fevers. In China it is used for leprosy.
Its principal use now is in the manufacture of incense and pastilles. It is also used in plasters and might be substituted for Balsam of Peru or Balsam or Tolu. The inhalation of steam laden with the volatile portion of the drug is said to relieve bronchitis and laryngitis.
The ceremonial incense of the Jews was compounded of four 'sweet scents,' of which pure frankincense was one, pounded together in equal proportion. It is frequently mentioned in the Pentateuch. Pure frankincense formed part of the meet offering and was also presented with the shew-bread every Sabbath day. With other spices, it was stored in a great chamber of the House of God at Jerusalem.
According to Herodotus, frankincense to the amount of 1,000 talents weight was offered every year, during the feast of Bel, on the great altar of his temple in Babylon. The religious use of incense was as common in ancient Persia as in Babylon and Assyria. Herodotus states that the Arabs brought every year to Darius as tribute 1,000 talents of frankincense, and the modern Parsis of Western India still preserve the ritual of incense. 
- Frankincense: More than an Ancient Herb, CBN News, Health & Science