Burning incense releases a complex mix of fragrant smoke that can subtly affect your mood, but it also fills indoor air with fine particles and chemical compounds at levels that pose real health concerns. The practice has been part of religious, spiritual, and personal rituals for thousands of years, and the science behind what that smoke actually does to your body is more detailed than most people realize.
What Incense Smoke Contains
When incense burns, it doesn’t just release a pleasant scent. The combustion process produces fine and ultrafine particulate matter, volatile organic compounds (VOCs), other gaseous compounds, and trace heavy metals. Researchers screening the gaseous emissions from various incense products identified 13 compounds of concern, including benzene, formaldehyde, toluene, styrene, naphthalene, and acrolein. Of these, benzene and formaldehyde were found at levels above World Health Organization guideline values in the majority of products tested. Both are classified as carcinogens.
The particulate matter is especially significant. Burning incense indoors can increase fine particle concentrations (PM2.5) by up to 120%. In one study of residential homes in Hanoi, the average PM2.5 during a burning session reached about 201 micrograms per cubic meter, with one-minute peaks spiking to over 825. For context, the WHO recommends keeping 24-hour average PM2.5 exposure below 15 micrograms per cubic meter. In poorly ventilated spaces, concentrations have been recorded as high as 1,850 micrograms per cubic meter.
How It Affects Your Mood
The calming or uplifting feeling people report from incense isn’t purely psychological. A compound found in frankincense resin, called incensole acetate, activates a specific type of ion channel in the brain involved in sensing warmth. In a study published in The FASEB Journal, researchers found that this compound produced measurable anti-anxiety and antidepressant-like effects in mice by triggering these channels. Mice that had been genetically modified to lack the channel showed no such behavioral changes, confirming the compound was responsible. The researchers suggested this mechanism could explain the mild euphoric or comforting feeling people associate with burning frankincense during religious ceremonies.
Not all incense contains frankincense, though. The hundreds of incense varieties on the market use different plant resins, essential oils, wood powders, and synthetic fragrances. Whether a particular stick or cone produces mood-altering effects depends entirely on its ingredients.
Effects on Brain Function
Beyond the short-term mood effects, long-term incense use appears to have a subtler impact on the brain. A study of community-dwelling older adults found that regular incense users showed decreased connectivity in a brain network called the default mode network, which is active during rest, daydreaming, and self-reflective thinking. Specifically, connectivity was reduced in brain areas responsible for spatial awareness, self-referential thought, language processing, and memory retrieval.
Proper functioning of this network matters for switching between focused attention and internal thought. Disruptions to it have been linked to various cognitive and psychiatric conditions. The researchers noted that while the changes were subtle, they were clearly measurable in people who burned incense regularly at home.
Respiratory Effects
The most immediate health effect of incense smoke is irritation of the eyes, nose, and throat. People who work in temples with heavy incense use have roughly four times the risk of throat and nose irritation compared to people who don’t. A survey of over 4,000 elementary school children in Taiwan found that incense burning at home was significantly associated with cough symptoms. Another study of more than 35,000 schoolchildren linked household incense use to increased childhood asthma occurrence.
The evidence isn’t perfectly consistent, though. At least one study of primary school children and their non-smoking mothers found no association between incense exposure and chronic respiratory symptoms like bronchitis, wheezing, or allergic rhinitis. The difference likely comes down to how much incense is burned, how often, and how well-ventilated the space is.
Cardiovascular Risk With Long-Term Use
The largest study on incense and heart health followed over 63,000 Chinese adults aged 45 to 74 for more than a decade through the Singapore Chinese Health Study. Researchers found that current long-term incense users had a 12% increased risk of dying from cardiovascular disease compared to people who never used incense or had stopped. The risk broke down to a 19% increase for stroke and a 10% increase for coronary heart disease. This was the first large-scale epidemiological study to document population-level cardiovascular effects from routine home incense use.
How Incense Compares to Cigarette Smoke
A comparison that surprises most people: in laboratory tests, the particulate matter from incense smoke showed greater ability to damage cells and DNA than the same dose of mainstream cigarette smoke. Researchers characterized the particles from two types of incense and compared them head-to-head with a reference cigarette using standard toxicity assays. All incense samples were more toxic to cells than the cigarette smoke, and one incense sample also showed higher genotoxicity, meaning it caused more genetic damage per dose.
This doesn’t mean burning a stick of incense is “worse than smoking a cigarette” in everyday terms. Cigarette smokers inhale deeply and directly, dozens of times per day, while incense smoke disperses through a room. But it does mean that the chemical composition of incense smoke is not harmless, and treating it as fundamentally different from other types of combustion smoke is a mistake.
Reducing Your Exposure
If you burn incense and want to keep doing so, ventilation is the single most important factor. Opening a window or running an exhaust fan can dramatically reduce the particle concentrations that build up in an enclosed room. Burning fewer sticks, choosing shorter sticks, and not burning incense daily all reduce cumulative exposure.
The type of incense matters too, though research comparing specific product types is limited. Charcoal-based incense has already undergone a carbonization process, which in theory means a cleaner burn with fewer volatile gases and tars. Wood-dust-based incense, which hasn’t been carbonized, tends to release more of those byproducts during combustion. No rigorous head-to-head studies exist yet, so choosing between the two is more informed guesswork than settled science. What is clear is that any incense burned in a small, poorly ventilated room will produce particle levels well above what health guidelines consider safe.