Scented candles, incense and essential oils: what they do to indoor air

Cosy rooms, low lighting and a “clean” scent in the air.

The setting seems ideal, until someone asks what people are actually breathing in.

Scented candles, incense and diffusers have become almost a welcome-home ritual: a sign of care, attention and “good energy”. Yet behind the promise of purifying a room, these habits can turn household air into a cocktail of unwanted substances, often at higher levels than those found on the busy street outside.

The myth of a healthier home that smells like a spa shop

Lighting a candle after cleaning, burning incense before bed or adding essential oil to a diffuser to unwind: it all appears harmless. The issue begins when this “freshly cleaned home” scent becomes a daily, long-lasting habit.

In reality, every flame, ember or warmed drop releases compounds that do not simply remain in the room. They enter through the lungs, circulate through the body and may irritate the airways, eyes and skin.

Indoor air can contain higher concentrations of pollutants than outdoor air, especially when candles, incense and oils are used together in enclosed spaces.

More concerning still, many people use these products precisely to “improve” the air - to neutralise food, cigarette or damp smells - without realising they may merely be replacing one nuisance with another that is less obvious and far quieter.

What candle flames and incense smoke really release

A large proportion of retail candles are made from paraffin, a petroleum-derived material. When burned, it produces fine particles and volatile organic compounds, including benzene and toluene, which are linked to respiratory irritation and, over time, greater risks for people who already live with chronic conditions.

Incense blends resins, sawdust, fragrances and binding agents. Its smoke contains ultrafine particles that can travel deep into the lungs. The impression of a “zen” space contrasts with heavily laden air that continues to circulate for hours, even after the stick has gone out.

Popular products such as scented papers and fragrance tablets work in a similar way: rapid combustion, a powerful aroma and a complex chemical mixture. The assumption that something containing resin, herbs or plants is automatically safe because it is “natural” does not hold up under laboratory analysis.

Essential oils: natural, but not always harmless

Essential oils are often marketed as a healthy alternative to candles and industrial sprays. They do originate from plants, but that does not make them risk-free. Used excessively or heated too strongly, they can release irritating molecules and worsen allergies.

• Lavender and citrus oils can trigger irritation in sensitive people.
• Some oils are toxic to cats, dogs and birds.
• Diffusers left running for hours raise the concentration of compounds in the air.

“Natural” does not mean “without risk”. Dose, duration of exposure and ventilation make all the difference to how the body responds to aromas.

When a “clean” scent becomes a health issue

Most often, the effects develop gradually and are mistaken for tiredness, stress or dry air. Complaints reported by allergists and respiratory specialists include:

• recurring headaches at the end of the day;
• stinging eyes after burning a candle or incense;
• a blocked nose with no obvious cause;
• wheezing in people with asthma;
• skin irritation in people handling concentrated essential oils.

Children, older people and those with rhinitis, asthma or heart conditions are generally the first to notice the effects. However, cumulative exposure is also a concern for healthy adults, particularly in small, poorly ventilated flats where several fragranced products are used every day.

Product	Main risk	Safer use
Scented paraffin candle	Fine particles, benzene, toluene	Choose a plant-based, dye-free option; use it briefly with an open window
Incense	Dense smoke, ultrafine particles	Use infrequently in a well-ventilated area, away from children and animals
Scented paper/fragrance tablet	High emissions over a short period	Burn only occasionally, never in a closed bedroom
Heated essential oils	Allergenic molecules, toxicity to pets	Use cold diffusion, only a few drops, for short periods and with ventilation

The mistake almost everyone makes with candles and incense

The biggest misconception is not using these products, but viewing them as air “purifiers”. Candles, incense and oils do not clean anything: they merely cover existing smells while adding new substances to the mix.

When scent takes priority over air quality, a home can smell lovely… and become more polluted at the same time.

Another easily overlooked factor is the combined effect of multiple sources. A modern home may contain room spray, scented disinfectant, heavily fragranced fabric conditioner, liquid soap “with long-lasting fragrance”, a scented candle and a reed diffuser - all operating together in spaces that often lack adequate ventilation.

How to use less fragrance and breathe better

Before buying anything, the first step is straightforward: open a window. Renewing the air daily, even for only a few minutes, dilutes indoor pollutants from the kitchen, bathroom, furnishings and, of course, fragranced products.

Practical guidelines for anyone who wants to keep the ritual

• Favour plant-wax candles made from soya or coconut, or beeswax candles, without dyes and with mild fragrances.
• Avoid burning incense every day; treat it as an occasional gesture rather than a routine.
• Choose cold essential-oil diffusers, using short cycles of 15–20 minutes in a ventilated space.
• Never leave any scented product burning or switched on in closed bedrooms, especially children’s rooms.
• Read labels: fewer ingredients are usually preferable to long, unclear lists.

For anyone seeking a pleasant home with fewer chemicals in the air, a few simple options work well: dried flowers, cotton sachets filled with citrus peel, coffee beans in open pots in the kitchen, and bicarbonate of soda in discreet containers to absorb damp odours.

When marketing conceals the smell of smoke

Terms such as “purifies the air”, “detox environment” and “lighter air” are common on packaging. Regulation of household fragrances remains fragmented and, in many cases, does not require a full breakdown of the substances used to create the scent.

This allows products with the same chemical base as ordinary deodorisers to be sold with a “natural” appeal simply because their visual branding refers to plants, crystals or ancestral rituals.

From the “cleaning smell” to healthy air: what changes in practice

A genuinely healthier home usually has fewer layers of scent, not more. The nose may find this unusual at first, as many people have become used to associating strong fragrance with cleanliness, but the adjustment is quick.

One useful exercise is an “aromatic detox” period: stop using candles, incense, sprays and diffusers for two weeks; improve ventilation; deal with any potential sources of mould or accumulated rubbish; and use cleaning products with little or no fragrance. Headaches, heavy-feeling eyes and a blocked nose may ease without anyone needing to change their mattress or medication.

Another rarely discussed issue is the cumulative effect. An occasional lit candle does not have the same impact as three fragranced products running daily in a small flat. Considering the “total fragrance load” can help people adjust their habits, particularly in homes with babies, older people or animals.

Ultimately, olfactory luxury may lie in simplicity itself: a clean, minimally ventilated home with the natural smells of the household - food, wood and plants - plus the occasional scented ritual used in moderation, rather than as a permanent crutch to disguise problems that need a different solution.