Allethrin

The evidence

• Volatile pyrethroid spatial repellents for preventing mosquito bites: a systematic review and meta-analysis
  2025Meta AnalysisDefinitive evidence

  This is the most rigorous look at the whole category to date: a systematic review and meta-analysis that pooled data from 58 eligible publications on volatile pyrethroid spatial repellents, the airborne-emanator products built on actives such as transfluthrin, metofluthrin, and allethrin. For 50 of those studies the authors combined individual mosquito-level records, more than 1.7 million mosquitoes in total, along with satellite weather data on temperature, humidity, and wind, so they could estimate an overall protective efficacy and see how it shifts by product format, active ingredient, mosquito species, and indoor versus outdoor setting. This is the single best study for setting honest expectations about what these devices deliver on average.

• An Expert Review of Spatial Repellents for Mosquito Control
  2020ReviewWell-supported evidence

  This is a commissioned expert review, not a single experiment, that pulled together the published evidence on spatial repellents. Spatial repellents are the family of products that put a volatile insecticide into the air around you rather than on your skin, which is the category that includes battery or heat-powered emanators such as Thermacell and the OFF! Clip-On, passive strips, and the older mosquito coil. The review walks through how these devices work, which airborne active ingredients drive them, and what protection they have delivered in controlled and semi-field testing, with the goal of judging whether the category is promising enough for public-health investment.

• Environmental health risks and benefits of the use of mosquito coils as malaria prevention and control strategy
  2018ReviewWell-supported evidence

  The mosquito coil is the oldest and cheapest airborne repellent device, a spiral you light so that it smolders and releases a pyrethroid such as allethrin or pyrethrins into the air. This review weighed both sides of the coil: how much it actually protects against mosquitoes, and what the smoke does to the people breathing it. It is a helpful reality check for anyone reaching for coils as a low-cost area repellent, because it puts modest efficacy next to a real air-quality cost.

• Field evaluation of an area repellent system (Thermacell) against Phlebotomus papatasi and Ochlerotatus caspius in Sanliurfa Province, Turkey
  2003Field TrialWell-supported evidence

  This was an outdoor field trial of the Thermacell area repellent, the butane-heated device that warms a mat holding allethrin so it drifts into the surrounding air. Researchers ran it in a village in Sanliurfa Province in southeastern Turkey and measured how much it cut biting from two different pests at once: Phlebotomus papatasi, a sand fly that spreads leishmaniasis, and Ochlerotatus caspius, a floodwater mosquito. Volunteers acted as bite collectors so the team could compare landing and biting rates with the device running versus without it.

Products using it

Thermacell

Thermacell Patio Shield MR300 Mosquito Repeller

71

Allethrin 21.97%

Coverage & effectiveness

Protected zone~15 ft zone

Fewer bitesest.70–92%

Thermacell

Thermacell Backpacker Mosquito Repeller

71

Allethrin 21.97%

Coverage & effectiveness

Protected zone~15 ft zone

Fewer bitesest.70–92%

Coghlan's

Coghlan's Mosquito Coils

43

Allethrin 0.25%

Coverage & effectiveness

Protected zone~5 ft zone

Fewer bitesest.30–60%

PIC

PIC Mosquito Repellent Coils

42

Allethrin 0.25%

Coverage & effectiveness

Protected zone~5 ft zone

Fewer bitesest.30–60%

Regulatory notes

Source: EPA SRS active ingredient list export. Minimum risk (25(b)) status is applied separately when applicable.