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August 25, 2023

What do we know about insect repellents?

As mosquitos and midges rise in the summer months, insect repellents can be an important safeguard for our health – but how much do we know about them? 


Most of us will have experienced the discomfort of insect bites at some point, so there will be times when we reach for some protection. But it’s unclear how insect repellents work, but insects may dislike the smell, and the active ingredients are thought to create a barrier that insects can’t smell, keeping them away from us! 


What chemicals are used in insect repellents? 

Diethyl Toluamide (DEET) is the most widely used chemical ingredient in formulations applied directly to the skin. It repels rather than kills insects; it’s thought that insects find it harder to smell humans when applied dermally. DEET was developed in the 1940’s by the American military to fight mosquitos and first appeared in the consumer space in the 1950’s; it’s used by millions of people around the world now.


DEET is considered to give the longest protection hours against the broadest range of pests. Our skin absorbs around 20% of this chemical when applied. 


Insect repellent clothing and textiles 

Where additional protection is needed, Permethrin is an insecticide used in some clothing and camping gear to deter insects. It belongs to the group of chemicals called pyrethroids which are thought to have neurotoxic effects and may cause skin and eye irritation.  


How safe are insect repellents? 

DEET is approved for use in most European countries and considered safe by the American Environment Protection Agency based on current scientific knowledge. It can cause skin irritation, but this is quite rare. Most data on potential harmful effects of DEET arise from overexposure or ingestion rather than absorption through the skin, but it has been implicated as a potential neurotoxic agents in animal studies.


The research we’ve found is a little dated, but of particular concern in children as it has been linked to seizures and respiratory distress. Other side effects include; redness, itching, burning, dermatitis, cardiovascular toxicity, acute manic psychosis, seizure and toxic encephalopathy. However, it must be noted that these are rare if applied as recommended and with appropriate use. 


How to use insect repellents  

Most insect repellents are applied by spraying or rubbing them onto skin, but it’s advisable to spray onto the hand before applying because of the risk of inhaling the chemicals used, especially with children. Most manufacturers advise against using insect repellents for children under 2 years of age.


Check the concentration of active chemical ingredients and choose the strength based on how long you think you need protection. For example, DEET at 10% concentration is estimated to give 2 hours of protection, and 30% gives up to 5 hours, but anything over 50% doesn’t increase efficacy. Most products display an Insect repellents factor IRF – higher scores offer longer protection. Apply after sunscreens.

Non chemical alternatives to reduce exposure to biting insects 

If you are concerned about about of the possible side effects of chemical based insect repellents, here are some ideas to consider.

  • Avoid spending time outdoors and dusk, especially at peak insect season and avoid using perfumes and scented soaps/lotions/hair products as they may attract biting insects.
  • Wear protective clothing, especially children and infants. Wear long sleeves, trousers and cover ankles and feet when in an area you may be bitten.
  • Candle infused with citronella may have some effect, although releasing the fragrance via a diffuser has been found to be more effective. Neal’s Yard sells a citronella spray but it’s not known how effective it is.
  • Oil of lemon eucalyptus (OLE) trees has been found to be effective, reducing mosquito attraction by 60%.
  • Lavender essential oil contains up to 35% linalool, a naturally occurring monoterpene alcohol that is found in many plants including citrus. Linalool is the active chemical compound in essential lavender oil have some insect repelling properties.
  • Incognito stock a range of insect repellent spray and lotions which are DEET free, vegan, 100% natural and NHS approved, clinically proven with 7 hours protection.
  • Neem oil (2-3ml) mixed with coconut oil has been shown to offer protection against bites from mosquitoes for 8 hours when applied to exposed areas.
  • Use mosquito nets when travelling to areas known to have higher levels of mosquitoes.  


It’s important to note that plant-based formulations do not last as long and need to be applied more frequently, and they may also not be effective for everyone.

Further Reading 

Plant-based insect repellents: a review of their efficacy, development and testing | Malaria Journal | Full Text (


Government information on Lyme disease 



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