Incense is burnt in aromatherapy sessions and religious ceremonies, during meditation, or to release a pleasant scent and mask bad odours. It is also used for spiritual purification or mystical cleansing purposes, and is sometimes employed as a fumigant to repel insects. Direct burning (combustible) incense is commonly sold in the form of cones or joss sticks, while indirect burning (non-combustible) incense is burned on top of a heat source such as coal embers or is granulated to form a powder or paste. Demand has also grown for scented candles as an air freshener and mood enhancer following the use of essential oils in aromatherapy.
Two of the best known aromatic resins used as incense are Frankincense (Olibanum) and Myrrh due to their religious associations with the Christian nativity, but others include Benzoin and Opopanax. In addition, Gums such as Tragacanth or Gum Arabic are used to bind the mixture of fuel and oxidiser within the incense, sustaining its ability to burn and release the fragrant materials or essential oils in its smoke. Shellac is also used in the micro-encapsulation of fragrances and perfume oils.