The trouble with DEET

New research on DEET health risks

DEET, the active ingredient in many insect repellents used by some 200 million people every year, appears to affect proteins in mammals as well as mosquitoes and other target insects. Some previous studies have implicated DEET in seizures among children. A new study (PDF) by an international group of scientists, supported by Agence Nationale pour la Recherche in France, published August 5 at BioMedicalCentral.com (BMCBiology), reports that DEET "is not simply a behaviour-modifying chemical but that it also inhibits cholinesterase activity, in both insect and mammalian neuronal preparations." Symptoms of lowered levels of cholinesterase, an enzyme essential to proper nervous system function, can include nausea, headaches, convulsions and, in extreme cases, death. Health risks increase when DEET and other pesticides are used together. The researchers concluded that "DEET is commonly used in combination with insecticides and we show that deet has the capacity to strengthen the toxicity of carbamates, a class of insecticides known to block acetylcholinesterase." The new findings are "consistent with previous studies, says Bahie Abou-Donia of the Duke University Medical Center in Durham, NC," speaking to Science News. Abou-Donia's research found increased toxicity when DEET and chlorpyrifos, an organophosphate insecticide hazardous by itself, were used together. "These effects should be clearly labeled on products containing DEET, or N,N-diethyl-3-methylbenzamide," says Abou-Donia. In Canada, he noted, "insect repellents can contain no more than 30 percent DEET. The United States - where 100 percent DEET repellents are available - should consider such restrictions."

- Pesticide Action Network of North America

Mosquito Repellants and Deterrents

Some Insects of British Columbia

Mosquito Repellents and Deterrents

Word has it that this is the worst summer in a long time for mosquitoes. I guess I should say it's a very good year for mosquitoes and a bad year for humans and other warm-blooded mammals. It's also a good year for swallows and other flying insectivores, including dragonflies. "Dragonfly naiads consume mosquito larvae in the breeding waters, and adult dragonflies eat adult mosquitoes." (Wikipedia). Which brings me to the helpful part of this post:
[Updated version here]

Mosquito Deterrents: This is the best information I could find. I certainly haven't tested all of these recommendations so use your own judgement and feel free to let me know directly, or as a comment below, what your experience or knowledge is.

NOTE: It is generally agreed that for most reliable protection, (e.g. where West Nile Fever is a risk) the best product is DEET. Note that DEET can damage synthetic fabrics and there are questions about its effect on the human body. The American Academy of Pediatrics recommends that repellents used on children contain no more than 10% DEET - and not at all on children under two months. Lotions can be applied more effectively than sprays. Don't use with sunscreen because DEET should not be re-applied. Wash off after use.

A. On/in your body:

1. Vitamin B-1 (Thiamine Hydrochloride 100 mg): 1 tablet a day.
   
2. No bananas: They make your body odour more attractive to the little ladies (yes, remember it's the females that bite).
   
3. Clothing: Wear long-sleeve shirts and pants
   
4. Oil of eucalyptus: at 30% concentration prevents mosquito bites for about 2 hours (New England Journal of Medicine)
   
5. Garlic juice: Mix 1 part garlic juice with 5 parts water in a small spray bottle. Shake well before using. Spray lightly on exposed body parts. Lasts 5 - 6 hours (or as long as your friends can stand you).

B. In/around the home:

1. A fan or gentle breeze: Mosquitoes don't like moving air
   
2. Strips of cotton cloth dipped in garlic mixture (see above): and hung in areas, such as patios, as a localized deterrent.
   
3. Sage or rosemary: on the barbecue coals
4. Herbs (When the leaves are crushed): wormwood, lemon grass, lemon thyme, pelargonium and citronella.
   
5. Mosquito nets: Not a common site in Canada but, properly used, are very effective and (in the long run) cheap.
6. Bat houses and swallow nesting boxes: They have to eat a lot though as mosquitoes make up less than 3% of a swallow's diet and less than 1% for a bat. (Christian Back, medical entomologist)
7. Standing water: Remove where possible, and change pets' dirinking water and birdbaths frequently.
8. Incense and coils: only use coils outdoors (e.g. not in tents) and regular incense indoors.
9. Shepherd's Purse: In the early spring, sprinkle the seed on water where mosquitoes breed. The mucilage of the seed will kill the larvae and greatly reduce mosquitoes in the area. One pound of seeds destroys ten million larvae, though it may cause a proliferation of shepherd s purse! (Dr Terry Willard, Wild Rose College of Natural Healing)