Incense and ritual fumigation

What it is

The burning of aromatic plant material — resin, wood, seed, bark or leaf — to mark a place or an act as sacred, and the enormous family of practices built on it.

It is worth being exact about the word, because it does different work from the words around it. "Incense" names a material. It is a substance you can buy, weigh and analyse, and burning it commits you to nothing. "Smudging" names a ceremony — a specific set of practices belonging to particular Native North American nations, with protocols about who conducts it and why. The two are constantly used as synonyms in shops, and they are not the same kind of word at all. That distinction, and why it matters, is the subject of smudging and ritual cleansing.

What both belong to is ritual fumigation, which is close to a human universal. It appears independently in Egypt, Mesopotamia, the Levant, India, China, Japan, Mesoamerica, sub-Saharan Africa, Aboriginal Australia and pre-Christian Europe, in traditions that had no contact with one another. The practice is common property. Particular ceremonies inside it are not.

Where it came from

The resin trade is old enough to have shaped the map. Frankincense and myrrh come from trees of the genera Boswellia and Commiphora that grow in southern Arabia and the Horn of Africa, and demand for them in Egypt, Mesopotamia, Greece and Rome sustained overland caravan routes from roughly the seventh century BC. UNESCO's Land of Frankincense sites in Oman preserve the Dhofar end of it. Pliny the Elder complained that the trade was draining Roman silver eastward, and put a number on it that historians still argue about.

Egypt supplies the earliest detailed record. Temple incense — kyphi — was a compounded preparation of resins, wine, honey and aromatics, and recipes survive inscribed on temple walls at Edfu and Philae. Around 1470 BC Hatshepsut sent an expedition to the land of Punt and brought back living frankincense trees, an event recorded in relief at Deir el-Bahari and among the earliest documented plant-collecting expeditions anywhere.

Jewish Temple practice specified a compounded incense, the ketoret, in Exodus 30, with the formula reserved for sacred use. Christian liturgy inherited censing from that world; the thurible is standard in Catholic, Orthodox and Anglo-Catholic worship, and most Reformation churches rejected it, which is why incense reads to many Western eyes as a marker of a particular kind of Christianity rather than of Christianity as such.

In East Asia the material and the practice arrive together with Buddhism. Incense is recorded in China from the Han period, and the Song-dynasty literati developed an elaborate connoisseurship around it. A Japanese chronicle records driftwood agarwood washing ashore at Awaji in 595, and by the Muromachi period incense had been formalised into kōdō, the way of incense, which sits alongside tea and flower arranging as one of the classical Japanese arts. Its practitioners speak of listening to incense rather than smelling it, and its games involve identifying and distinguishing woods.

In South Asia, dhoop and agarbatti are integral to temple and domestic worship, and India is now the largest producer of stick incense in the world. In Mesoamerica, copal — resin from Bursera and related trees — was burned in Maya and Aztec ceremony and continues in Indigenous and folk Catholic practice today.

How it is done

Three forms, and they are genuinely different technologies.

Loose material on coals is the oldest and the simplest: grains of resin or chips of wood placed on charcoal or hot ash in a censer. Everything before the modern period is essentially this, and it is still how frankincense is burned in a thurible and how copal is burned in Mexico.

Compounded sticks, cones and coils are later. Indian agarbatti are made by rolling paste onto a thin bamboo splint; Japanese and Chinese sticks are extruded solid with no core, which is why they leave no bamboo smell. Coils were developed to burn for many hours unattended.

Heating without burning is the refinement. In kōdō a fragment of agarwood is placed on a small mica plate over buried charcoal in ash, so the wood is warmed to release its aromatics and never combusts. There is no smoke to speak of, which is the point.

This page describes the practice and its history. It contains no recipes and no ritual instruction, and the ceremonial protocols of living traditions are not detailed here.

What we can and cannot say

We can say the smoke is a genuine air quality problem, and this is better documented than most people expect. Burning plant material indoors produces fine particulates, carbon monoxide, volatile organic compounds and polycyclic aromatic hydrocarbons, and measured particulate concentrations in unventilated rooms during incense burning are high. Cohort work has found associations with respiratory symptoms and, in the Singapore Chinese Health Study, with upper respiratory tract cancers among long-term domestic users. Studies of temple workers with heavy daily exposure point the same way.

The honest framing is exposure and ventilation rather than prohibition. Occasional burning in a ventilated room is a different proposition from a stick a day in a closed flat, and the people most affected are those with asthma or other respiratory conditions, and anyone burning it occupationally.

We can say there is a small antimicrobial literature and that it does not prove what it is cited for. A 2007 study by Nautiyal and colleagues found substantial reductions in airborne bacterial counts in a closed room after burning medicinal smoke. That is a real measurement. It says nothing about whether the practice benefits anyone, and it is not evidence for any claim about energy, atmosphere or spiritual cleansing.

We can say the conservation picture is severe, and that it is worse here than for the plants people usually worry about.

Agarwood is the extreme case. It is not a wood the tree ordinarily makes: Aquilaria trees produce the dark aromatic resin only in response to wounding and fungal infection, so a harvester cannot tell from outside which tree contains any. Large numbers are felled to find few, and wild oud is among the most valuable raw plant materials on earth. Aquilaria malaccensis is listed in the Herbarium as CITES Appendix II and IUCN Critically Endangered. Cultivated and artificially inoculated plantation agarwood now exists and is the straightforward alternative.

Frankincense is declining too. Boswellia populations across the Horn of Africa and India are under pressure from over-tapping, grazing and land-use change, and published projections of falling production have been alarming enough to prompt industry attention. Myrrh is in a comparable position. Sandalwood was depleted across much of its Indian range and is now substantially supplied from Australian plantations.

We can say the word "incense" conceals an enormous range of things. At one end is a lump of tapped tree resin. At the other is a bamboo splint coated in sawdust, charcoal and a synthetic fragrance oil, which contains none of the plant it is named after and burns a different set of compounds. Both are sold as incense, the price difference is large, and the label rarely distinguishes them. Anyone choosing on either aesthetic or health grounds is choosing between two substantially different products.

And we can say what the difference from smudging actually is, since that is the question that brings most people here. Incense is not restricted. No tradition holding it has asked outsiders to stop, its commercial trade is largely conducted by the cultures that developed it, and nobody was prosecuted for burning frankincense. Native American ceremony was actively suppressed in the United States into the twentieth century and only explicitly protected in 1978. That asymmetry — not the plant, not the smoke, not the sincerity of the person burning it — is what makes one contested and the other ordinary.

We cannot say whether smoke carries anything upward. What can be said is that the impulse to send something fragrant into the air at an important moment is one of the most widely and independently attested things people do, that the materials it depends on are finite and several are in trouble, and that the practice has always been about the material as much as the meaning — which is why the trade routes came first.

Further reading

• Nigel Groom, Frankincense and Myrrh: A Study of the Arabian Incense Trade.
• David Oller and the kōdō literature in translation, for the Japanese art.
• CITES listings for Aquilaria and Santalum, which are public and searchable.
• The Singapore Chinese Health Study publications on domestic incense exposure.