(WXIA) -- With bug-biting season in full swing, there's good reason to be bugged by insect repellent.
Consumers must weigh the risks of getting a bug bite with the risks of chemicals engineered to keep them away and there's no completely safe and sure way to prevent bug bites.
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But some repellents are effective and low in toxicity, as long as users follow directions, especially for children, says a new guide by the Environmental Working Group, an environmental advocacy non-profit.
The report - a collection of data from the Environmental Protection Agency, the World Health Organization, and the Centers for Disease Control and Prevention - identifies four active ingredients that can provide safe and effective protection: Picaridin, DEET, IR3535, and Oil of Lemon Eucalyptus. According to the report:
• Picaridin isn't odorous and irritating like other chemicals and it provides all-day protection from mosquitoes and ticks at 20% concentration, but it's not as effective as the most common repellent, DEET, some studies show.
• DEET is commonly maligned for neurological damage, seizures, and eye irritation, but can provide all-day protection at concentration of 20%-30% against a variety of pests. The EWG says that DEET is a "reasonable" choice when weighed against the consequences of Lyme disease and West Nile virus, adding that the chemical's safety profile is better than assumed. In 1998, the EPA concluded the rate of adverse reactions was very low - 1 per 100 million people.
• The chemical IR3535 has a good safety profile, but like DEET, it can cause eye irritation, melt plastic, and damage fabric. It's also not effective unless it's used in concentrations higher than 20%.
• Extracts from the Eucalyptus tree were the most effective botanical ingredient. Though the extract - which has the trade name Oil of Lemon Eucalyptus - can provide up to six hours of protection at 30% concentration, it can irritate lungs.
Higher concentrations provide longer protection, not better protection. Consumers should steer clear of products with more than 30% DEET and avoid any bug repellent on children less than 6 months old, the EWG says.
Bug zappers, fogger insecticides, candles, and aerosol sprays can trigger respiratory problems, contain toxic ingredients, and may not be effective, studies show.
Experts expect the number of bug-borne illnesses to rise as the warming climate expands the habitats of species that spread pathogens.
Lyme disease cases more than doubled over the last 15 years, with over 24,000 confirmed reports in 2011. West Nile virus - the most common mosquito-borne disease threat in the United States - infected more than 5,600 people last year, resulting in over 1,500 deaths since 1999, the CDC says.
Parents can take a few safety precautions before lathering themselves and their kids with chemicals, the EWG says. Cover exposed skin by wearing pants, long sleeves, socks, and shoes, use mosquito netting especially for kids going off to camp, and get rid of mosquito breeding grounds like standing water, the CDC advises.
The CDC says any product with Oil of Lemon Eucalyptus should not be used on children under 3 years old. When safely using bug spray, parents should spray their hands then apply it to young children.
What about expecting and nursing mothers? The CDC reports that pregnant women and new moms nursing may safely use bug repellent without any additional precaution.
According to the EPA, repellents should be used with caution. Repellents should not be sprayed between clothing and skin, nor should they be sprayed on cuts, wounds or irritated skin.
Because these recommended ingredients aren't fail-safe, it's important to be flexible and responsibly choose the type and concentration of repellent based on the area's risk of bug-borne illnesses.
"If in a certain location or for a specific person a product is not working, a different active ingredient can be tried," said David Andrews, lead author of study and EWG senior scientist.
Few data confirm the effectiveness and safety of bug repellents from natural extracts, thanks to a 1996 loophole in EPA regulations that exempted 31 pesticide ingredients or "minimum-risk pesticides" from safety and efficacy testing. The exemption gave companies a faster path to market for pesticides of lower toxicity concern, Andrews said.
While data vary widely, the EWG warns these extracts rarely work for long periods of time and often contain human allergens at much higher concentrations than personal care products.
These products can advertise protection against mosquitoes and ticks, just not mosquitoes and ticks that cause West Nile virus or Lyme disease. Common natural repellents contain castor, clove, geraniol, lemongrass, rosemary and soybean oil.
The EPA is considering requirements for products to provide data about their effectiveness in order to avoid natural products from masquerading with the EPA's stamp of approval, Andrews said.
The science behind the effectiveness of all repellents is as varied as its application, said Gabe Hamer, a clinical assistant professor at Texas A&M University who has studied insect repellents.
With more than 3,000 species of mosquitoes worldwide, repellents don't protect against all bug and mosquito species. Other variables like location, time of day, wind speed, and the subjects involved can shift efficacy, Andrews said.
Sweat and water could also wash away repellents, making it difficult to tell if a repellent is effective, said Joseph Colon, an adviser for the American Mosquito Control Association.
The CDC reports that the higher the percentage of the active ingredient, the longer protection lasts. However, when you get your first bite or two, it is likely time for another application of repellent.
Plus, the CDC recommends avoiding heavy application. It will not protect the skin better, and multiple light applications work best for a longer lasting shield.
USA TODAY contributed to this report.