Choosing an Insect Repellent

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For most people, insect bites are a minor annoyance.
The area may swell and itch for a while and then return to normal later.
This mild reaction is caused by the venom the insect carries and it normally occurs with the bite of a mosquito, fly, cockroach or bedbug.
In this case, vinegar, diluted ammonia or phenolated calamine lotion will relieve itching and burning.
Other insect bites can also be cleaned with alcohol, povidone-iodine or plain soap and water.
These simple measures, however, cannot protect people from the many diseases insects bring, some of which are life-threatening.
If that's your concern, it may be a good idea to buy an insect repellent.
Thiamin or vitamin B1 has long been recommended for this purpose.
Isolated reports say that large amounts of thiamin taken by mouth make perspiration offensive to insects, driving them away.
To get this effect, dermatologists say you should take 150 milligrams of thiamin three to four times a day.
Good as it sounds, that formula doesn't work.
The US Food and Drug Administration said that as early as 1960, thiamin was found to be ineffective as an insect repellent.
In that experiment, volunteers took as much as 200 milligrams of thiamin three times a day and exposed their forearms to hungry female mosquitoes.
The result: everyone got bitten in spite of the thiamin they took.
In choosing an insect repellent, look for a product with N,N-diethyl-meta-toluamide or deet for short.
This chemical was first synthesized in the 1950s and remains the most effective repellent against a wide variety of crawling and flying pests.
Concentrations of up to 95 percent were used by American troops during the Vietnam War and many manufactures have incorporated deet in their insect repellents since 1961.
Deet's performance depends on how much is used.
A product that contains more deet is more effective and can ward off mosquitoes for over six hours and stable flies for over 4 1/2 hours.
Tests made by Consumer Reports also showed that deet performed well against two of the most common and troublesome species of mosquitoes - the Aedes aegypti which causes dengue or H-fever, and Culux pipiens which causes filariasis.
But that protection comes with a price.
Since deet is absorbed in the bloodstream, higher concentrations of this chemical can cause serious side effects.
"Among the most dramatic instances: six girls under age nine developed toxic encephalopathy, a swelling of the brain that can cause disorientation, convulsions and death.
Three of the girls died.
Deet repellents had been applied copiously to most of the girls for weeks or months, and one girl had metabolic disease that apparently made deet's effects worse.
But another victim had been wearing insect repellent for just two days.
More recent reports have noted brief seizures in five males - four boys under age eight and one adult - after they used deet repellent of varying concentrations, typically only once or twice daily," according to Consumers Reports.
(Next: The trouble with deet.
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