A study in The New England Journal of Medicine compares a range of common insect repellents on the market and their effectiveness. Allergist Dr. Clifford Bassett of New York University Medical Center visits The Early Show with the details.
The study found that DEET-based products were the most effective, new natural soybean and eucalyptus oils also worked well. Citronella was much less effective and wristband products did not work at all.
The most effective and widely marketed insect repellent is DEET with a four to five hour protection period at 23.9% concentration. Lesser concentrations still provided two to four hour protection.
The soybean oil product protected for about an hour and a half.
Citronella products all protected under twenty minutes, some as little as three minutes.
Wristbands were ineffective regardless of the ingredient.
While many people are confused about how to select insect repellents, Dr. Basset suggests this rule of thumb: Choose products with a concentration of 10% or less DEET for children and a concentration of 10 to 20% DEET or greater for adults. For people who react to side effects from DEET that can include skin rashes, headaches and dizziness, other natural products that contain eucalyptus or soybean oils can also effectively repel insects.
For activities such as backyard picnics and barbecues, mosquito coils which last up to four hours and keep a 10x10-foot area essentially mosquito free are recommended.
For "high-risk" activities such as camping, fishing and hiking, insect repellents with a 20% or higher concentration of DEET are best.
There has been a lot of controversy and testing of the chemical repellent DEET and its possible adverse health effects. In recent years, DEET-less products have come on the market because of concerns about the chemical's safety, especially for children.
After exhaustive testing, the EPA has concluded that as long as consumers follow label directions and take proper precautions, repellents containing DEET do not present a health concern, even for children. Cases of adverse effects were mostly the result of overuse and improper use, such as rubbing the product near or in the eyes. The EPA recommends keeping DEET products away from cuts, wounds or irritated skin. For kids, it should be kept away from hands and mouths.
With kids you should always apply repellent to your own hands and rub it on, do not apply it directly to the face. With DEET the strength is about how long the effect lasts not the level of protection.
Always read the label for proper indications and usage. Apply sparingly only to exposed skin or preferably clothing to avoid skin irritation, additional usage does not increase effectiveness, one application may last four or more hours.
Avoid applying high concentration products directly to the skin, especially for children. Do not inhale or get in the eyes. Avoid exposure to children's hands to prevent eye and mouth contact. Never use repellent on wounds or irritated skin. Wash repellent-treated skin after returning indoors. If skin irritation occurs, call your doctor.