Incense is composed of aromatic biotic materials, which release fragrant smoke when burned. It is used in religious ceremonies, ritual purification, aromatherapy, meditation, for creating a mood, and for masking bad odours.

Incense is composed of aromatic plant materials, often combined with essential oils. The forms taken by incense differ with the underlying culture, and have changed with advances in technology and increasing diversity in the reasons for burning it. Incense can generally be separated into two main types: “indirect-burning” and “direct-burning.” Indirect-burning incense is not capable of burning on its own, and requires a separate heat source. Direct-burning incense is lit directly by a flame and then fanned or blown out, leaving a glowing ember that smoulders and releases fragrance. Direct-burning incense comes in several forms, including incense sticks cones, and pyramids.

Types

Incense materials are available in various forms and degrees of processing. They can generally be separated into “direct-burning” and “indirect-burning” types depending on use. Preference for one form or another varies with culture, tradition, and personal taste. Although the production of direct- and indirect-burning incense are both blended to produce a pleasant smell when burned, the two differ in their composition due to the former’s requirement for even, stable, and sustained burning.

Indirect-burning Incense

Indirect-burning incense, also called “non-combustible incense.” It is a combination of aromatic ingredients that are not prepared in any particular way or encouraged into any particular form, leaving it mostly unsuitable for direct combustion. The use of this class of incense requires a separate heat source since it does not generally kindle a fire capable of burning itself and may not ignite at all under normal conditions. This incense can vary in the duration of its burning with the texture of the material. Finer ingredients tend to burn more rapidly; while coarsely ground or whole chunks may be consumed very gradually as they have less total surface area. The heat is traditionally provided by charcoal or glowing embers.

• Whole: The incense material is burned directly in its raw unprocessed form on top of coal embers.
• Powdered or granulated: The incense material is broken down into finer bits. This incense burns quickly and provides a short period of intense smells.

Direct-burning Incense

Direct-burning incense also called “combustible incense.” It generally requires little preparation prior to its use. When lit directly by a flame and then fanned out, the glowing ember on the incense will continue to smoulder and burn away the rest of the incense without continued application of heat or flame from an outside source. This class of incense is made from a moldable substrate of fragrant finely ground (or liquid) incense materials and odourless binder. The composition must be adjusted to provide fragrance in the proper concentration and to ensure even burning. The following types of direct-burning incense are commonly used:

• Coil: Extruded and shaped into a coil without a core. This type of incense is able to burn for an extended period, from hours to days, and is commonly produced and used by Chinese culture
• Cone: Incense in this form burns relatively fast. Incense cones were invented in Japan in the 1800s.
• Solid stick: This stick incense has no supporting core and is completely made of incense material. Easily broken into pieces, it allows one to determine the specific amount of incense they wish to burn. This is the most commonly produced form of incense in Japan and Tibet.
• Loose powder: The incense powder used for making indirect burning incense is sometimes burned without further processing. They are typically packed into long trails on top of wood ash using a stencil and burned in special censers or incense clocks.
• Rope: The incense powder is rolled into paper sheets, which are then rolled into ropes, twisted tightly, then doubled over and twisted again, yielding a two-strand rope. This type of incense is highly transportable and stays fresh for extremely long periods. It has been used for centuries in Tibet and Nepal.

Direct-burning incense of these forms is extruded, pressed into forms, or coated onto a supporting material.

The disks of powdered mugwort called ‘moxa’ sold in Chinese shops and herbalists are used in Traditional Chinese medicine for moxibustion treatment. Moxa tablets are not incenses; the treatment relies on heat rather than fragrance.

Health Uses

Incense smoke contains various contaminants including gaseous pollutants, such as carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides(SOx), volatile organic compounds (VOCs) [4–8], and absorbed toxic pollutants like polycyclic aromatic hydrocarbons and toxic metals. The solid particles range between 10 and 500 nm. The emission rate decreases in the row Indian sandalwood, Japanese aloeswood, Taiwanese aloeswood, smokeless sandalwood.

Research carried out in Taiwan in 2001 linked the burning of incense sticks to the slow accumulation of potential carcinogens in a poorly ventilated environment by measuring the levels of polycyclic aromatic hydrocarbons (including benzopyrene) within Buddhist temples. The study found gaseousaliphatic aldehydes, which are carcinogenic and mutagenic, in incense smoke.

A survey of risk factors for lung cancer, also conducted in Taiwan, noted an inverse association between incense burning and adenocarcinoma of the lung, though the finding was not deemed significant.

Frankincense has been shown to cause antidepressive behavior . It activated the poorly understood ion channels in the brain to alleviate anxiety and depression.