Mosquito Coils and Incense: Do They Work, and Is the Smoke Safe?

A single natural incense stick burning in a ceramic dish on a wooden garden terrace at dusk, surrounded by potted plants and lanterns

Key takeaways

  • Coils do reduce nuisance biting in a small, still space: a systematic review of 15 controlled trials found positive anti-mosquito effects for more than 95% of the outcomes measured.
  • They have never been shown to prevent disease. The same review found no trial showing that burning coils prevents malaria.
  • The smoke is the real concern indoors. Laboratory measurements estimated that one coil can release as much fine particulate matter (PM2.5) as 75–137 cigarettes.
  • Burn coils and incense outdoors only, upwind of where you sit, and treat them as a background extra — not as a replacement for a skin repellent, screens or a net.
  • For reliable personal protection, health authorities point to skin-applied repellents with an approved active such as DEET, picaridin, IR3535 or PMD.

Mosquito coils and repellent incense are a summer ritual on patios, campsites and holiday balconies across Europe, Asia and Africa. They are cheap, they smell like holidays, and they seem to work. But do mosquito coils actually work, and is the smoke safe to breathe? Here is what the evidence says — including the parts the packaging tends to leave out.

How do mosquito coils and repellent incense work?

A classic mosquito coil is a spiral of dried paste (often wood powder, starch and a binder) impregnated with an insecticide. When the tip smoulders, it releases the active ingredient into the air as a vapour and fine smoke. Most commercial coils use pyrethroids such as d-allethrin, transfluthrin or metofluthrin.

The airborne active works in three ways, depending on the dose:

  • Spatial repellency — mosquitoes avoid the treated air and fly elsewhere.
  • Feeding inhibition — they stay nearby but are less likely to land and bite.
  • Knockdown — at higher concentrations, they are temporarily paralysed or killed.

Plant-based incense sticks work differently. They usually contain no synthetic insecticide; instead they release aromatic plant compounds (lemongrass, citronella and similar oils) together with smoke. Their effect is milder and more local, which is why they are best understood as creating a less inviting atmosphere rather than a protective barrier.

Do mosquito coils actually work?

Partly — and the details matter. In 2004, a systematic review in the Journal of Travel Medicine pooled 15 controlled trials of insecticide coils. Of 38 separate outcomes (bite reduction, repellency, knockdown, mortality), more than 95% showed a positive anti-mosquito effect. So, in the right conditions, coils genuinely reduce the number of bites.

The same review, however, found no controlled trial showing that coils prevent malaria. A later Cochrane review of repellents for malaria prevention (2018) likewise concluded that the evidence for spatial repellents protecting against malaria was insufficient. Reducing nuisance biting on a terrace is not the same as protecting you from a mosquito-borne infection.

Why the effect is so variable

  • Wind — a light breeze carries the vapour away; a coil upwind of you helps, one downwind does almost nothing.
  • Distance — protection is concentrated within a metre or two of the coil.
  • Open space — on an open beach or a large garden the vapour disperses too quickly.
  • Burn time — once the coil or stick goes out, the effect stops within minutes.
  • Species — some mosquitoes, such as the day-biting Asian tiger mosquito, bite low around the ankles, below where the smoke drifts.

Is mosquito coil smoke harmful?

This is where the picture changes. Burning anything produces smoke, and smoke indoors is a health issue in its own right. A study in Environmental Health Perspectives (2003) measured emissions from common coil brands and found that, under realistic room conditions, pollutant levels could substantially exceed health-based air-quality guidelines. The researchers estimated that burning one coil releases as much PM2.5 as 75–137 cigarettes, and as much formaldehyde as up to 51 cigarettes. The particles were ultrafine and fine — the size that reaches deep into the lungs.

A 2016 survey of coil users in Ghana, published in Malaria Journal, recorded self-reported complaints such as coughing, eye irritation and headaches. The World Health Organization identifies household air pollution from burning fuels and materials indoors as a significant cause of respiratory and cardiovascular disease, particularly for children.

Who should be most careful

  • Babies, young children and pregnant people
  • Anyone with asthma, COPD or other lung or heart conditions
  • Pets, especially birds, which are very sensitive to airborne irritants
  • Anyone sleeping in a small, closed room with a coil burning

The safety rule is simple: never burn coils or incense in a closed bedroom, and do not leave them burning overnight. If you want a mosquito-free night, a well-fitted screen or a bed net does the job without any smoke — see our guide on how to keep mosquitoes out of your bedroom at night.

Coils, incense and other options compared

Method Reduces bites? Coverage Main drawback
Insecticide coil Yes, in still air 1–2 m around the coil Smoke and fine particles; not shown to prevent disease
Plant-based incense stick Mild, local effect Small outdoor area Smoke; weaker than an insecticide coil
Plug-in vaporiser Yes, in a closed room One room Needs electricity; still an airborne insecticide
Bed net or window screens Yes, very effectively Bed or room Only protects while you are inside
Skin-applied repellent Yes, on treated skin Moves with you Needs reapplying as directed on the label

The pattern is clear: methods that act on the air around you are sensitive to wind and space, while methods that act on your skin or physically block mosquitoes travel with you. Gadgets that promise protection without either — such as wristbands or buzzing apps — tend to perform worst of all; we looked at the evidence in do mosquito wristbands and ultrasonic apps work?

How to use coils and incense more safely

  1. Outdoors only. Patios, gardens and campsites — never in closed rooms or tents.
  2. Place them upwind and close to where you sit, ideally at ankle-to-knee height.
  3. Keep smoke away from faces, children and pets, and on a heat-proof stand away from anything flammable.
  4. Put them out when you go inside — never leave them burning unattended or overnight.
  5. Combine them with a skin repellent and covering clothing at dusk, when many mosquitoes are most active.

How incognito® helps

We see coils and incense as an optional extra for outdoor evenings, never as your main protection. For personal protection that goes wherever you go, our Insect Repellent Spray is DEET-free and uses PMD (Citrepel®), a plant-based active derived from Java citronella (Cymbopogon winterianus). It is clinically proven, recommended against mosquitoes and ticks, vegan and biodegradable — and it produces no smoke at all.

If you enjoy the ritual of a scented evening outside, our Incense Insect Repellent Sticks are made from parawood, lemongrass and coconut oil with zero plastic packaging. Use them the same way as any incense: outdoors, in a well-ventilated spot, away from children and animals — alongside a skin repellent, not instead of one.

FAQs

Do mosquito coils really work?
Insecticide coils reduce nuisance biting within a metre or two in still air, according to a review of 15 controlled trials. They do not protect a whole garden, and no trial has shown that they prevent malaria or other mosquito-borne diseases.

Is it safe to burn a mosquito coil indoors?
It is best avoided. Measurements show that one coil can release as much fine particulate matter as 75–137 cigarettes, and indoor smoke is a known respiratory risk. Use screens, a bed net or a plug-in device designed for indoor use instead.

Can I sleep with a mosquito coil burning?
No. Leaving a coil burning in a closed bedroom overnight means hours of breathing smoke, plus a fire risk. A bed net or window screens protect you all night without either problem.

Are natural incense sticks safer than insecticide coils?
Plant-based sticks avoid synthetic insecticides, but any burning material produces smoke and fine particles. Use them outdoors in a ventilated spot, away from faces, children and pets.

Are mosquito coils safe around babies and pets?
Keep coil and incense smoke well away from babies, young children and pets, especially birds. For babies, physical barriers such as nets over cots and prams are the safest first line of protection.

What protects better than a mosquito coil?
A skin-applied repellent with an approved active such as DEET, picaridin, IR3535 or PMD protects you wherever you move, and screens or nets protect you indoors. Coils are at best a supporting extra outdoors.

Sources

This article is for general information only and does not replace medical advice. If you have a respiratory condition, are pregnant, or are travelling to an area with mosquito-borne disease, talk to your doctor or a travel clinic. Always read the product label before use.