QI: some quite interesting facts about incense Frankincense is a tree resin (or dried tree sap) from the Boswellia tree, native to Oman and the Arabian Peninsula. It was highly valued for medicine - fly repellent, stomach soother, cough remover, blood thinner, cold medicine, joint-oiler - and for its scent, as incense. It was an important component of the Ketoret, the Jewish incense offering and is mentioned several times in both the Old and New Testaments. From 3000BC to AD 1500, the main source of the resin was Oman. Nowadays, little Omani frankincense is exported because bulk buyers (such as the Roman Catholic Church) go for cheaper Somalian varieties. Pure frankincense is edible and may even have anti-cancer applications. Its English name means "incense of the highest quality" (franc meaning noble, or free - the Franks being the ruling class in post-Roman Gaul). Bitter Whereas frankincense has a sweet fragrance, myrrh, another tree resin, is bitter and spicy. It is harvested from Commiphora myrrha, a small, thorny tree native to Yemen, Somalia and eastern Ethiopia. Its name comes from the Arabic murr meaning "bitter." At times, worth more than its weight in gold, myrrh is one of the spices used in the Ketoret and in the Christian anointing oil known as "the oil of Chrism" (Chrism was Greek for an "anointing" and both "Messiah" and "Christ" mean "anointed"). It is also an important element in traditional Chinese and Ayurvedic medicine, possessing powerful antiseptic qualities. The Ancient Egyptians used it to embalm mummies. Fishy Ambergris is a strange aromatic substance excreted by sperm whales. It is produced in their stomachs, where it coats indigestible bits of cuttlefish and squid, the whale's main prey. Inside the whale, ambergris is black, sludgy and foul smelling. Outside it oxidises into a waxy grey substance used as a fixative for rare perfumes, as it makes them last much longer. A single drop of ambergris will remain fragrant on the pages of a book for 40 years. For many years its provenance had proved a mystery. The Japanese believed it was dragon spit that had drooled into the sea. In the West it was thought to be the sperm of fish or seabird droppings. The Chinese were the first to appreciate the flavour, and sprinkled it as powder on their tea; the Egyptians melted globules of it into their coffee; King Charles II liked it grated over his eggs. Its reputation as an aphrodisiac was recently confirmed by Dr Paolo Sandrino in Minnesota in 2001, who discovered that eating ambergris increased testosterone levels. Warm The most popular of all aromatic woods, the 25 members of the Santalum family, are found in India, Indonesia, Australia and the Pacific Islands. Its warm, distinctive scent has made it an essential part of the rituals of Hinduism, Buddhism, Zoroastrianism and Chinese and Japanese religions. Trees take 14 years to mature, but the cut wood can keep its fragrance for decades. As a result, real sandalwood commands more than £10,000 a ton and has spawned a multimillion-pound black market in Western Australia, now the world's largest producer. Practical Joss sticks are incense-coated sticks burned in China and India, often in front of the thresholds to homes or businesses, as a propitiatory offering to the spirit of the place. The word "Joss" is a Chinese pidgin version of the Portuguese word for God - deus. Buy 1,227 QI Facts to Blow Your Socks Off by John Lloyd, John Mitchinson, & James Harkin (Faber & Faber, RRP £9.99) from Telegraph Books (0844 871 1515) An expanded fully updated version of the QI App for iPad and iPhone is available now at theqiapp.com at £2.99