Today, we'll help you sort through repellent options.
Fortunately, Washington's mosquitoes — so far — are merely annoying pests whose bites raise itchy welts that eventually go away. But that could change with mosquito-borne West Nile virus disease, a form of encephalitis (brain infection).
The disease, which originated in Africa, first appeared in New York City in 1999 and has been gradually moving west, now as far as Iowa. Experts say it almost certainly will reach Washington, possibly as early as this summer and probably within a year.
Most infected people have no symptoms, and even fewer become seriously ill. Yet fatalities are possible. Eighteen American deaths have been reported since 1999.
But even where mosquitoes can't give you a disease, you'd probably just as soon avoid the bites and itch. That means checking out possible defenses.
Repellents — DEET or Don't?
Among repellents, the main choice is between those that contain the chemical N,N-diethyl-3-methylbenzamide (also called N,N-diethyl-meta-toluamide), or DEET, and those that don't.
Virtually every expert agrees that DEET is the most powerful mosquito repellent developed so far. But because of health questions, there's also a following for DEET-free products, such as citronella.
However, as the Journal study confirmed, their protection is generally shorter-lasting than DEET's.
"DEET has had a remarkable safety profile after more than 40 years of use and nearly 8 billion human applications," said Dr. Mark Fradin, co-author of the Journal study.
But DEET has been associated with a small number serious reactions — 50 documented in medical literature — including seizures, and extremely rarely, death from encephalopathy, a brain inflammation. A rash or blisters can also occur.
Toxicity cases have frequently involved excessive use or misuse of DEET, Fradin said.
"With any drug or intervention, we look at risk versus benefits," said Dr. Christopher Sanford, a University of Washington travel-medicine expert.
He believes DEET's benefits outweigh risks, especially for anyone traveling to tropical or subtropical countries where mosquito-borne diseases such as malaria or dengue fever pose a serious hazard.
For himself, Sanford chooses DEET whether there's disease risk or not, even to fend off the Northwest's more benign bugs.
He said the "holy trinity" of mosquito defense includes DEET on exposed skin, protective clothing (long pants and sleeves), and head and bed netting.
Safety for children
DEET safety questions often center on infants and children. Use on infants is "a gray area," with little scientific data available, said Sanford. Because babies have more skin surface relative to body weight, their bodies may absorb relatively more DEET than an adult's would.
Better than using DEET on a child under the age of 2, he said, would be to reduce the baby's exposure to mosquitoes.
For children older than 2, Sanford considers DEET safe, though he would choose products with DEET concentrations no higher than 20 percent (others advise 10 percent). For adults, 20 to 35 percent will do the job. Concentrations range up to 100 percent.
Health Canada, that nation's chief health agency, recently decided to ban products containing more than 30 percent DEET.
Also weighing in is Duke University pharmacology professor Mohamed Abou-Donia, who says his numerous rat studies indicate that frequent and prolonged DEET use can adversely affect brain cells affecting movement and memory. His studies include two published last year, in the journal Experimental Neurology and the Journal of Toxicology and Environmental Health.
Abou-Donia believes use should be sparing, infrequent and of short duration.
The Environmental Protection Agency says DEET is generally safe but does not allow DEET product labels to claim child safety, saying there's no data to support such claims.
The most common DEET advice: Don't use it on infants or pregnant women, use infrequently and in low concentrations on children older than 2, and avoid excessive use or very high concentrations on yourself.
Many products besides DEET claim to fend off mosquitoes. Some work, others don't. Results may vary with individual users. Following is a sampling.
• Botanical repellents: Though DEET generally out-performs these, two ranked near the top in the Journal article.
As noted, oil of eucalyptus offered the third-longest protection; the Journal article mentions two brands, Repel Lemon Eucalyptus and Fite Bite Plant-Based Insect Repellent.
The other high-placing botanical was Bite Blocker for Kids, made with soybean oil.
Besides these, citronella generally gets better reviews than other plant-based repellents.
Of the many other plants used in botanical repellents — cedar, peppermint, lemongrass and geranium, to name a few — the Journal article said most gave only brief protection in preliminary tests.
Repellent wrist bands, with either citronella or DEET, did not fare well.
Avon Skin-So-Soft: Though this product was developed as a bath oil, consumers discovered it repels mosquitoes. Tests confirm that, but protection is brief, requiring repeated applications.
Garlic; vitamin B1: Though some people swear by these, experts say there's little data supporting their effectiveness.
Some advocates suggest taking B1 for a few weeks before visiting a mosquito-dense area.
The vitamin or garlic won't hurt you as long as you avoid megadoses (as with any supplement), but don't rely solely on them when serious mosquito-fighting measures are needed.
There are zillions more home remedies — from clove oil to avocado oil; few have solid supporting data.
Permethrin: This insecticide (not a repellent) is sprayed on the outside of clothing — not on skin — killing mosquitoes (and ticks) that land on it; it's usually only used where mosquito density is high or where these insects can carry disease.
Federal reports say permethrin has low toxicity in mammals. But some research suggests that very long use (60 days or more), especially when combined with DEET, might cause adverse neurological effects.
Outdoor devices: mosquito coils, citronella candles, electronic "zappers," ultrasonic devices, mosquito traps: Of these, the smoke-emitting coils are considered most effective. Citronella candles get mixed reviews.
Zappers lure and then electrocute insects (both helpful and harmful kinds), but tests indicate mosquitoes are more attracted to humans than to zappers.
Ultrasonic devices, which emit high-pitched sounds (inaudible to humans) that supposedly repel mosquitoes, have been generally debunked.
New and expensive ($200 to $1,300) mosquito traps are designed to attract and trap mosquitoes, but they're not effective enough to warrant the cost, contends an environmental biologist, Jim Rindfleisch, quoted by Knight Ridder Newspapers.
Rindfleisch oversees mosquito control for York County, Va., and has tested the traps, which are marketed in catalogs and online. |
