University of Illinois Extension


John Church
Extension Educator, Natural Resources
Rockford Extension Center

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Use Mosquito Repellents Appropriately

With concerns about West Nile Virus, many people are more cautious about trying to avoid mosquito bites. Reducing the population and breeding sites around the home is a good practice, but you may still need to wear protective clothing and use repellants. The most effective repellents contain DEET (N,N-diethyl-m-toluamide). DEET has been tested against a variety of biting insects and has been shown to be very effective and is recommended by the Center for Disease Control.

The question of which DEET formulation to use often comes up. The more DEET a repellent contains, the longer the time of protection provided from mosquito bites. A higher percentage of DEET in a repellent does not mean that the protection is better, just that it will last longer. Based on studies, a product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites. A product containing 20% DEET provided almost 4 hours of protection. A product with 6.65% DEET provided almost 2 hours of protection. Products with 4.75% DEET and 2% soybean oil were both able to provide roughly 1 ½ hours of protection.

A higher percentage of DEET should be used when a person will be outdoors for several hours while a lower percentage of DEET can be used if time outdoors will be limited. It can be re-applied if you are outdoors for a longer time than expected and start to be bitten by mosquitoes. Choose a repellent that will be likely to be used consistently and that will provide sufficient protection for the amount of time that will be spent outdoors. Product labels often indicate the length of time that protection can be expected from a product.

Use enough repellent to cover exposed skin or clothing. Do not apply repellent to skin that is under clothing. Heavy application is not necessary to achieve protection. Do not apply repellent to cuts, wounds, or irritated skin. After returning indoors, wash treated skin with soap and water. Do not apply aerosol or pump products directly to your face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.

Always follow all label directions when using a chemical product, especially if using on children. If there are questions about a product’s safety, consult an appropriate person such as a physician or pharmacist prior to use.

More information on west nile virus in humans and pets and the use of mosquito repellants, chemical and non-chemical, can be found at U. of I. websites and

June - July 2005: Last Issue | Use Mosquito Repellents Appropriately | Diseases and Insects of Shrubs and Small Trees | Garlic Mustard

Past Issues

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