How Does Insect Repellant Work?

How Does Insect Repellant Work?
How Does Insect Repellant Work? (Image: Robin L. Jessie-Green)

Active Ingredients

Insect repellents are made of various chemical composites. There are man-made chemical formulas as well as natural oils derived from plants used to create repellents. Common active ingredients in synthetic insect repellents are DEET (N,N-diethyl-m-toluamide) and Picaridin (KBR 3023) (CDC, 2008). Natural repellents are made of oil of lemon eucalyptus, citronella oil, lemongrass and geranium (Heal & Surgeoner, 2003). All repellents work by discouraging insects from landing and climbing on treated surfaces, and therefore, biting treated skin. Repellents are not pesticides or insecticides and do not kill insects.


Both synthetic and natural insect repellents are effective at deterring insects, preventing their bites by disrupting their ability to detect protected surfaces. However, synthetic repellents last longer. Synthetic repellents are longer lasting because of their high concentration of active ingredients. Products containing 20 to 23.8 percent DEET provide 4 to 5 hours of protection from mosquito bites. Some plant-based repellents made of essential oils can be short-lived because they wear off or evaporate completely within 2 hours. However, you need to reapply both types of insect repellent if you perspire or get wet (Vertellus, 2008).

Follow Instructions

Read the label for instruction on how to apply your chosen insect repellent. There may be age restrictions and cautions for avoiding certain parts of the body such as eyes, nostrils and mouth. Certain high potency synthetics like Permethrin should only be applied to clothing and gear, while oil of lemon eucalyptus must only be used on people over the age of 3 years. By properly using insect repellents, you create a protective barrier that will keep insects at bay (NPIC, 2007).

Prepare Insect Repellent

Shake the can or bottle of insect repellent and apply to cover exposed skin or clothing. There is no need to apply the product to skin already covered by clothes. Avoid excessive application of the insect repellent. It is not necessary and may cause harm if too much is absorbed or inhaled. If you are using a spray, note the spraying distance specified on the container. If using oil, note how much should be applied and whether it requires rubbing into the skin or laying it on the surface.

Apply Repellent

By applying an insect repellent directly on the skin, clothing and gear, the scent repels insects and arthropods from the immediate area. The reach of the repellent does not extend much farther than beyond the area sprayed. Because insect repellents are effective at short distances, insects may still be in the vicinity in spite of the use of a repellent.


One of the most important reasons to use insect repellents is to ward off female mosquitoes. They bite animals and people for protein found in blood, which helps in the development of mosquito larvae. Insect repellents work by "masking human scent," or through emitting a scent insects typically avoid. Because insects such as mosquitoes are attracted to odors emitted by the skin and carbon dioxide from breath, repellents work by covering or neutralizing the alluring scent, making a person unattractive for feeding (CDC, 2008).

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