Tips on how to avoid getting bitten by mosquitoes

By Melissa Patrick
Kentucky Health News

Spending time outdoors is one of the great pleasures of summer. Unfortunately, this is also the active season for the 50 mosquito species that call Kentucky home. These mosquitoes are more than just a nuisance; some carry disease, making it important to protect yourself from them.

Photo from cdc.gov

Chikungunya is the latest mosquito-born virus transmitted in the U.S., although most cases in the U.S. are still caused by infections acquired from travel to the Caribbean, South America or the Pacific Islands, according to the federal Centers for Disease Control and Prevention. It is rarely fatal, but commonly causes fever, severe joint pain and other symptoms.

Kentucky had 17 confirmed cases of Chikungunya last year as well as eight probable ones, all in residents who had traveled recently to the Caribbean. and none of the cases were fatal. The state also had three confirmed cases of other mosquito-borne illnesses in 2014, including two dengue fever cases and one West Nile case, according to the Kentucky Cabinet for Health and Family Services.

Repellents

Insect repellents are your best guard against mosquitoes.

Four products have been registered with the U.S. Environmental Protection Agency for use as mosquito repellents: DEET (diethyltoluamide), picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products.

Consumer Reports tested 15 products that represented each of these recommended repellents by spraying the products on the forearms of the testers, waiting 30 minutes, exposing their forearms to mosquitoes and ticks, and then measuring the number of bites every hour.

Based on this experiment, the magazine recommended Sawyer Fisherman's Formula (20 percent picardin) and Repel Lemon Eucalyptus (30 percent oil of lemon eucalyptus) as its first and second choice for repellents.

"It was the first time in the history of Consumer Reports testing insect repellents that the non-DEET formulations did better than the deet products," Sue Byrne, the magazine's senior editor of health and food, told Darla Carter of The Courier-Journal.

These products were followed by Repel Scented Family (15 percent DEET); Natrapel 8 Hour ( 20 percent picardin); and Off! Deepwoods VII (25 percent DEET).

Read the Labels

The U.S. Food and Drug Administration strongly recommends that you read the labels of all insect repellents before use and then use them as instructed, paying careful attention to the age limitations and precautions.

"As long as you read and follow label directions and take proper precautions, insect repellents with active ingredients registered by the U.S. Environmental Protection Agency do not present health or safety concerns," according to the FDA website.

Multiple sources say it is also important to not use combination products that contain both sunscreen and insect repellent. Sunscreen is meant to be applied often, while insect repellent is meant to be used sparingly.

High doses of DEET have been known to cause rashes, disorientation and seizures, according to the U.S. National Library of Medicine.

The FDA also notes that concentrations of any of the active ingredients above 50 percent "generally do not increase protection time" and that products with less than 10 percent of the active ingredient "offer only limited protection, about one or two hours."

Insect repellents and children

Adults should always apply insect repellents for children, making sure they don't get any on their hands, around their eyes, on any cuts or irritated skin. Spray repellents should always be applied outdoors, to avoid inhaling them.

The FDA recommends that DEET not be used on children under 2 months of age and that oil of lemon eucalyptus products not be used on children under 3 years old.

The American Academy of Pediatrics recommends that products with more than 30 percent DEET not be used on children, and that you use just enough repellent to cover exposed skin. It also recommends immediately washing off the repellent, and washing any clothes worn while exposed to the repellent, before wearing them again.

KidsHealth recommends that if you use DEET products on children, you should adjust the concentration of product by the number of hours your kids will be outside, using a lower concentration if they are only out for an hour or two and a higher concentration, which will last longer, if they will be out longer.

Non-repellent protections

In addition to advice on repellents, the University of Kentucky College of Agriculture, Food and Environment's Entomology Department website offers these suggestions to avoid mosquitoes:

• Minimize the standing water around your house; this is where mosquitoes breed.
• Use larvicides if it is impractical to eliminate a breeding site.
• Remove tall weeds and overgrowth in your yard; mosquitoes like to rest here during the day
• Keep windows, doors and porches tightly sealed and keep your screens in good repair.
• Stay indoors during the evening hours.
• Wear long-sleeved shirts and pants when outdoors.

UK Entomology says most devices that claim to attract, repel or kill mosquitoes don't work, or are unproven. It says "bug zappers" kill only a small percentage of mosquitoes, and studies have found that portable electronic devices using high-frequency ultrasonic sound are "of negligible benefit in deterring mosquitoes and reducing bites." The website does say that citronella oil offers "a degree of protection," but you need multiple candles to be effective.

Some odors we emit make us more attractive to mosquitoes; various repellents, including plant oils, are available

Mosquitoes are attracted to some people more than others because of skin odors or chemicals they emit, Jill Richardson writes for Salon. Carbon dioxide, heat, moisture, scent and appearance attract mosquitoes, but it's the chemicals you emit that make them want to take a bite, she writes.

Photo from Lexington Herald-Leader

Kentucky has about 60 of the 150 species of mosquitoes found in the U.S., according to the University of Kentucky Public Health Entomology Laboratory. Not all bite, and if one does, it is always a female, which needs the protein found in blood to make her eggs, UK extension entomologist Lee Townsend writes in The Courier-Journal.

Each species differs in biting persistence, habits and ability to transmit disease and even flying ability, Richardson writes, but it is the chemicals we emit that dictate their preference of who to bite.  L-lactic acid, ammonia, carboxylic acids and octenol, especially in combination with each other, are the chemicals most likely to attract them.

Scientist have found that adding l-lactic acid to the scent of someone who is not normally bitten by mosquitoes will make them more attractive to certain kinds of mosquitoes, Richardson reports. The presence of carbon dioxide has also been found in studies to be attractive to certain mosquitoes. Ammonia, which occurs from a pH change when bacteria in sweat multiply, is also appealing to mosquitoes.

So are smelly feet. Studies with Limburger cheese, which resembles human foot odor, have confirmed this. However, malarial mosquitoes are most attracted to this odor, so the saying that "If you keep your feet clean then mosquitoes won't bite," is good advice only if you are traveling in the tropics, Richardson writes.

Human odor that attracts mosquitoes may be genetically driven, but theories vary. One says individuals who are not attractive to mosquitoes don't produce the odors that attract them; and another says some people actually emit an inherited odor that keeps mosquitoes from finding them.

For those who consider themselves "mosquito bait," Richardson makes several suggestions: bathe at dusk, when mosquitoes come out, to minimize sweat odor, rub your body with antimicrobial plants like sage, wear a full-body mosquito net suit or use a repellent, which is the most convenienct, effective protection.

The most common repellent is DEET, available over the counter in many preparations. A prescription repellent is permethrin, which Richardson says may be carcinogenic though it is approved by the Environmental Protection Agency.

A young jewelweed plant

Many people use essential plant oils, though they evaporate quickly, requiring frequent application. The one most commonly recommended is lemon eucalyptus oil, which has proven effective. Richardson's article has details about other plant oils, and recommends crushed jewelweed as a remedy for mosquito bites.

Darla Carter of The Courier-Journal also had a good roundup of mosquito information in the Louisville paper's July 18 edition: http://www.courier-journal.com/story/life/wellness/health/2014/07/17/guard-mosquitoes-summer/12786213/.