We use medicinal plants in may ways. We drink them (infusion, decoction, flower essence, alcohol tincture, glycerine tincture, syrup, honey extract, oxymel), eat them (capsule, tablet, homeopathic pills, electuary, culinary spices, vegetables, pot herbs), absorb them through our skin (salve, lotion, poultice, mask, hydrosol, oil, ointment, balm, cream, compress, vapor rub, essential oils, ear drop, bath, soak, sitz bath), absorb them through our mucus membranes (suppository, sinus wash , enema, douche, eye drop), and utilize them in spiritual ways (talismans, charms, medicine bundles, smudges, incense). We also inhale their medicine through cigarettes, pipes, steams, essential oil diffusers, atomizers, and, yes, incense.
The medicinal effects of incense depend on our sense of smell. The process occurs when molecules travel up the sinus cavities, dissolve into the mucus lining, and are detected by the olfactory receptors on the tips of the olfactory sensory neurons. How these molecules are sensed is debatable as to whether the neurons are sensing the vibration of the molecules or their shape, with the theory alternating between the two ideas back and forth over the centuries. Either way, our sense of smell is very weak compared to other animals. For example, humans have 10 cm square of olfactory tissue in their sinuses, while dogs can have up to 170 square cm of olfactory tissue with a hundred times more receptors per square centimeter. Smell is the only sense perceived in right brain which is the side of brain focused on intuition and imagination, versus the left brain which is focused on analyzes and logic. Because of this the effects of smell are physical, psychoactive, and emotional. Interestingly, fragrance is considered to be the spirit of the plant and so affects our spirit. Smell is also processed through the limbic system, which deals with emotions, lust, hunger, memory, and imagination. This is why smell can trigger emotions and memories. Smell is also our oldest sense, part of the primordial "lizard brain" which is 450 million years old and predates other ancient senses like sight and balance.
There are records of the use of incense all over the ancient world. The oldest recorded use is in Egypt, although it was also used extensively in ancient times in other African countries, Arabia, India, the Americas, and Europe. The old Incense Road transported frankincense from southern Arabia on camel caravans north to the Mediterranean Sea and Europe and east to Mesopotamia and India. The Spice Trade of centuries past moved aromatic plants between Europe and the islands of Indonesia via the Red Sea and the monsoon winds. The Silk Road brought the use of incense along with Buddhism from India, through China and on to Japan in about the first century AD In fact, the incense ceremony (kohdo) is still considered to be one of the traditional Japanese arts, along with flower arranging (ikibana), tea ceremony (sado), and the Japanese lyre (koto). Formal incense schools were formed in Japan's Edo period, 1603-1867, although there was a decline of the incense ceremony in 19th century due to the disintegration of shogunate and feudal society, and the reopening of Japan and China to the west and the ensuing westernization . Fortunately, the craft and ceremony of incense was revitalized in the 1920's in Japan by descendants of the koh-do ("way of incense") masters, and in the 1960's incense schools began offering classes again.
Synthetic incense is very different in composition from natural incense. Synthetic incense is typically made with a binder, usually starch, a bamboo core, which produces copious smoke and adds the smell of burning bamboo, and ignition source such as charcoal, sodium nitrate, paraffin, or a petroleum solvent. The paraffin and petroleum solvents are especially harmful because they are neurotoxic and the inhalation of their smoke can cause asthma, skin reactions, nausea, dizziness, sneezing, and headaches. The smoke is also an irritant for the eyes, nose, and throat. Synthetic incense also typically contains synthetic aromas, 95% of which are derived from petroleum and cause the same symptoms listed above. These synthetic aromas are favored by certain manufacturers because they are lower in cost, more consistent, can be used to create novel scents not found in nature, and are an ethical substitute for ingredients from endangered species like musk, ambergris, and civet. However, synthetic aromas are not identical in complexity to natural scents so they can smell artificial. Furthermore, they do not have the same physical, emotional, and psychoactive properties of natural scents, and have the adverse effects noted above. Unfortunately, there are no legal restrictions on the quantities or combinations of synthetic fragrance chemicals, the ingredients of these synthetic aromas do not have to be listed, and only a fraction of them have been tested for safety.
Natural incenses, on the other hand, are usually 100% plant. In Japan, natural incense is made with a base of makko, aka tabu no ki. This is a water soluble, adhesive, odorless substance that burns smoothly and evenly. It is the powdered inner bark of Cercidiphyllum japonicum (Katsura Tree, Japanese Judas Tree), an evergreen in the Magnolia family, and functions both as a natural binder and as a source of ignition. Interesting to note is that the Magnolia family is the most primitive of all angiosperms (flowering plants), evergreen but with leaves, and the flowers form into cones similar to those found on conifers. The fossil record for these plants goes back to 100 million years! Other examples of plants in this family include cinnamon, cassia, bay laurel, champa, nutmeg, mace, star anise, ylang-ylang, camphor, avocado, mountain laurel, rhododendron, and magnolia. In India the traditional incense base is halmaddi, the resin of the Tree of Heaven, which has an unusual hygroscopic property (it pulls water out of the air) that makes Indian incenses feel damp to the touch. Hamaddi combined with honey, contributes the sweet honey / vanilla note to champa (spice mixture) incenses. To the base of makko and hamaddi is added ground and powdered herbs including resins, barks, flowers, seeds, roots, leaves, fruits, twigs, rhizomes, bulbs, woods, lichens, seaweeds, and animal ingredients like ambergris, musk, pangolin scales , and conch shells.
Incense is historically used for many different reasons, especially medical, ambient, and spiritual applications. Medicinal uses include boosting energy, treating and preventing illness (fumigation), inducing and promoting restful sleep, stimulating the libido, enhancing positive emotions, and a reduction of anxiety, stress, fear, worry, sadness, or anger. It is also used for ambiance, to clear and / or define a space, induction a certain mood along a group, to scent space, clothing, hair, or writing paper, to cover unpleasant odors, to inspire creativity, or to sharpen focus for study. Historically, before mechanical clocks, it was even used to track the passage of time during meditation, meetings, or at the geisha house. The spiritual uses of incense are many. For prayer the incense smoke is seen as a way to attract and please the gods, sweeten your prayers, and the rising smoke is said to carry both prayers and the spirit of the false up to heaven. Incense is also used spiritually to admit meditative states, dreams, and visions, and to help with focus during prayer. It can even improve the acoustics in churches and other large spaces and help one accept communications from plants. It purifications and sanctifies space, people, and ceremonial objects, and drives off evil spirits, insect pests, disease, and negative energy. It is used extensively to mark celebrations and rites of passage and is burned as a sacrifice itself. Finally, it is used to mask the smell of cremation and animal sacrifice.
Incense ingredients come from all parts of plants and have a wide variety of actions: bark, flower, fruit, leaf, resin, seed, and wood. Cinnamon is a commonly used bark that counters exhaustion, depression, and weakness, and tones and calms the nerves. Cloves are an example of a flower that is used (they are actually a flower bud) and they are considered to be a mental stimulant. Juniper berry, a fruit, stimulates and strengthens the nerves, strengthens the spirit in challenging situations, and relieves anxiety, nervous tension, and mental exhaustion. Eucalyptus leaf clears the mind and improvements concentration, while benzoin resin is calming and uplifting, comforts the sad and lonely, and acts as an anti-depressant and sedative. A common incense seed is fennel which boosts courage, resolve and strength in the face of adversity. Sandalwood, one of the most common bases for incense, is calming and harmonizing, reduces stress and tension, act as an antidepressant, and combats fear, stress, nervous exhaustion and anxiety.
In closing I would like to offer the "Ten Virtues of Koh." Koh is the Japanese word for incense and this list was compiled by a 16th century Japanese Buddhist monk: it brings communication with the transcendent, it purifies both body and mind., It cleanses and clarifies the spirit of worldly blindness, it brings alertness, it provides a companion in the middle of solitude, in the midst of busy affairs it brings a moment of peace, when it is plentiful, one never tires of it, when there is little, still one is satisfied, age does not change its efficiency, and used every day, it does no harm.