Mosquito Repellents and OrganochloridesInsect repellents have been around for thousands of years with evidence of their use by man dating back since before Egyptian times. And their employment doesn’t stop with mankind, for even animals such as the capuchin monkey have been observed rubbing a particular type of millipede into their hair which contains mosquito-repelling substances.

However, the safety of the chemicals man has used for repelling or killing mosquitoes, has been hotly debated – and none more so than a group of chemicals derived from chlorine.

Organochlorines and Organochlorides

Organochlorines and organochlorides (OCs) are a group of compounds which contain chlorine. Their primary use has been as a pesticide, of which the most well known are perhaps DDT, Aldrine and Lindane.

While the use of these chemicals was in some ways effective as pesticides, there was much concern over their harmful effects on the environment and adverse health effects.

OCs are now regarded as endocrine disruptors which mimic oestrogen and are linked to such medical issues as sterility, cancer, damage to the nervous system, and birth defects. Many have been banned in the UK although Lindane is still in use.


Lindane is an OC which has traditionally been used in pesticides and insecticides but is now widely restricted in some countries due to its persistence in the environment and suspected health effects.

Breast cancer is the most common type of cancer in women in the UK, with approximately 30,000 finding a malignant lump each year. The increase in this type of cancer has been associated in part with exposure to organochlorine chemicals including lindane, as residues of the chemical have been found in breast tissue and breast milk.

Because of the dangers of organochlorines, other chemical constituents are now used in mosquito repellents – although lindane remains an ingredient in solutions designed to treat head lice.


The most effective mosquito repellent today is still one first developed in the USA more than fifty years ago when intensive research was carried out to find a substance that could effectively protect soldiers from attack by pests during the Second World War. It is highly effective and is the benchmark by which other repellents are still measured, with around 15 million people using DEET-based repellents each year and about 200 million globally.

The main active ingredient is Diethyl-meta-toluamide or DEET, a chemical which can repel insects for some hours but which can cause adverse reactions in some people such as eye irritation, and skin problems.

The jury is still out on the use of DEET. While its effectiveness is indisputable and its great advantage is being to protect against malaria, the organic community feels that its use should be highly restricted and only used when absolutely necessary.

They base their opinion mainly on reports which state that if DEET is misused or over-used, then heavy exposure can cause fatigue, muscle and joint pain, breathlessness, headaches and memory loss.


Pyrethrins are compounds found in pyrethrum extract from chrysanthemum flowers and are therefore naturally occurring. The manufactured alternatives are pyrethoids which form the active ingredient in many repellents considered ‘safer’ to use than DEET based formulas and often promoted for children.

However, pyrethrins and pyrethroids are harmful to amphibians and fish and are a hot topic of debate in the USA at the moment after the Center for Public Integrity found that these ingredients were attributable to massively increased health problems and even deaths during the last decade.

Natural Mosquito Repellents

With the possible dangers of chemical mosquito repellents, it is always best to use a natural, organic deterrent where possible. Some of the traditional, effective methods include the use of the following:

  • Smoke
  • Citronella
  • Eucalyptus oils
  • Lemon grass
  • Peppermint

There are also other simple things you can do to prevent mosquitoes from biting you:

  • As far as you can, remove any standing water from your garden. Standing water provides a perfect breeding ground for mosquitoes, so make sure you don’t have any old water sitting in flower pots or bird baths.
  • Cover up. If you don’t want to be bitten, then make sure you wear appropriate clothing, especially at dusk in warm, still weather when mosquitoes are out in abundance.
  • If you live near somewhere which attracts a lot of mosquitoes then consider screening your windows or doors.