Did you know that mosquitoes can sense the presence of humans even from far away? They’re attracted to the heat, humidity and the carbon dioxide that are given off. Most mosquito repellents work by hiding the chemical cues that attract mosquitoes. A good repellent will offer protection for a long period of time after just one application. That’s important because many diseases like West Nile virus are transmitted by mosquitoes.

It’s important to remember that mosquito repellents do not protect everyone equally. Many factors are involved including the type of mosquito and the age, sex, and level of activity of the person involved. Remember too that mosquito repellent only works on the surface to which it’s applied directly.

The Center for Disease Control (CDC) recommends two products, DEET and picaridin. According to the CDC, each of these products works well and offers long lasting protection. DEET was developed in the 1940’s for the U.S. Army and first offered to the public in 1957.

Mosquito repellent products come in many concentrations. Which you choose will depend on how long you’re typically outside. If you’re usually out 3-4 hours, you might look for a product with 20% or more of DEET. However, scientists tell us that products containing more than 50% DEET do not offer extra protection. If you’re often outside for less than 3 hours a product with less than 20% DEET or 7% picaridin offers good protection.

How safe are these products? Here’s what the various agencies say. If used according to directions DEET does not pose any health problems, and is not considered a human carcinogen according to the Environmental Protection Agency (EPA). The CDC does not recommend sunscreens with combining products that contain DEET. DEET concentrations below 30% are safe for children two months of age and older according to the American Academy of Pediatrics.

The CDC recommends two other active ingredients that typically provide reasonably long protection, although not as long as the higher concentrations of DEET. They are oil of lemon eucalyptus and IR3535. Oil of lemon eucalyptus is a synthetic version of the real product. EPA’s testing indicates that oil of lemon eucalyptus provides protection similar to low concentrations of DEET. Read the label however, as that product should not be used on children under 3 years of age.

In spite of many scientific studies, there is no evidence that ultrasonic mosquito repellent devices work. Neither is there any evidence that eating garlic, vitamins, onions, or any other food will repel mosquitoes from people. It seems the portable traps that emit carbon dioxide are still too new for any decision from the scientists.

To use mosquito repellents safely, follow these guidelines: Always read the instruction and follow the directions. Apply these products only to exposed skin. Do not apply repellents to cuts, wounds or rashes. Do not apply near eyes or mouth. Apply only lightly around the ears. Never allow children to apply these products. Always wash or bathe to remove these products when you return indoors.