By: Michael Waldvogel and Charles Apperson, Extension Entomology

Biting insects, mites and ticks are a part of our environment. Whether we are hiking in woodlands or gardening in our backyard, we are potentially exposed to these pests. These bloodsucking animals are attracted to people by a number of chemical and physical factors, including carbon dioxide from our breath, body heat and, chemicals in our sweat and on the surface of our skin. Certain colors and textures of clothing and, even the odor from soaps, perfumes, lotions and hair care products may attract mosquitoes and some biting flies. When used sensibly, repellents will provide some personal protection from biting insects and mites. The following information is presented to answer some commonly asked questions about repellents and mechanical devices that allegedly repel insects and ticks.

The Centers for Disease Control and Prevention has recently added two more repellents to its list of recommended repellents:

• Picaridin, also known as KBR 3023, is an ingredient found in many mosquito repellents used in Europe, Australia, Latin America and Asia for some time. Evidence indicates that it works very well, often comparable with DEET products of similar concentration. One product, containing 7 percent picaridin, is being distributed in the United States for the first time this year.
• Oil of lemon eucalyptus (also known as p-menthane 3,8-diol or PMD) is a plant-based mosquito repellent that provided protection time similar to low concentration DEET products in two recent studies. It is available in a variety of formulations throughout the United States.
  Two important points of note about lemon-eucalyptus based products:
• According to the label, oil of lemon eucalyptus products should NOT be used on CHILDREN UNDER 3 YEARS OLD.
• The CDC's recommendation refers only to EPA-registered repellents containing the active ingredient oil of lemon eucalyptus (PMD). “Pure” oil of lemon eucalyptus (e.g. essential oil) has not received similar, validated testing for safety and efficacy nor is it registered with EPA as an insect repellent. Therefore, use of only the essential oil is not included in the CDC's recommendation.

• A variety of repellent formulations can be purchased from drug stores, supermarkets and sporting goods stores. With products containing DEET, the general "rule of thumb" is that products containing 10-30% active ingredient in the desired formulation (lotion, pump and aerosol sprays, etc.) should be effective.
  
  
• Apply repellents only to exposed skin and to clothing that insects can bite through. Never apply repellents to skin under clothing as this increases absorption of the chemical into the skin which in the case of some repellents may cause an adverse reaction.
  
  
• Use the minimum amount needed to cover your skin and/or clothing. Do not overdose yourself or your children. Avoid repeated application of repellents containing more than 50% DEET to skin over a short period of time.
  
  
• Recommendations for using DEET-based repellents:
  
  

  User's Age	Conc. of DEET	Application Instructions
  Six months to less than two years	10% or less	Apply only once daily
  Two years to less than 12 years	10% or less	Maximum of three applications daily
  12 years and older	30% or less	Follow label precautions

  
  
• When using repellents on children:
  • Never allow children to handle the chemical. Apply your hands and then spread it onto their skin for them.
  • If you're using a new repellent, you may want to apply it first to a small area on their arm to make sure they're not allergic to it (from a skin sensitivity perspective).
  • Do not put repellent on the hands of small children. They might rub their eyes or stick their hands in their mouths and ingest some of the chemical.
    
    
• Be careful when applying repellents to yourself. Repellents sprayed directly into the eyes will cause irritation and some formulations may damage eye glasses or other synthetic materials. Apply the chemical to your hands then carefully rub it onto your face.
  
  After returning indoors, wash treated skin with soap and water or bathe. This is particularly important when repellents are used repeatedly in a day or on consecutive days. Also, wash treated clothing before wearing it again.
  
  
• The CDC discourages the use products that combine a repellent and sunscreen because the instructions for using each of these components are different and sunscreens are often applied more frequently than a repellent should be.
  
  
• If you suspect that you or your child is having an adverse reaction to an insect repellent:
  • Discontinue using it immediately
  • Wash treated skin with soap and water
  • Call your local poison control center
    
    

    North Carolina Poison Control Center
    	Carolinas Poison Center Carolinas Medical Center PO Box 32861 Charlotte NC 28232-2861 Emergency Phone: 1-800-222-1222

    
    
  • If you go to a doctor, take the repellent container with you so the doctor can review the label information.
    

Another repellent, Permanone (permethrin), is applied to clothing only (not to your skin). It will repel most mosquitoes and biting flies, as well as fleas, ticks and chiggers. Some body lotions have been reported to repel biting insects. The ingredients in these lotions do not possess any repellent properties. Instead, the mineral oil in these products creates a barrier film that prevents the insect's mouthparts from penetrating the skin. These lotions are most effective against sand flies ("no-see-ums") and other biting insects with short mouthparts.

Other information about DEET is available at the following sites:

• Using Insect Repellents Safely. (USEPA)
• Mosquito Repellents (Mayo Clinic)
• Mosquitoes and Mosquito Repellents: A Clinician's Guide (Annals of Internal Medicine)
• Updated Information Regarding Insect Repellents (CDC)

Other repellent chemicals
Oil of Citronella, which is extracted from Andropogon nardus, has been used as a mosquito repellent since 1882. "Citronella candles" are commonly burned outdoors to repel mosquitoes and other biting insects from around porches, decks and picnic areas. The candles will be most effective when there is relatively little air movement that might disperse volatile chemicals too quickly.

Systemic repellents
Vitamin B1 (thiamine chloride), garlic, brewer's yeast and other plant-based chemicals have been reported to repel mosquitoes when taken orally. Some of these materials are marketed in tablet form, and the manufacturers claim that protection from mosquitoes will last up to 24 hours after taking one tablet. To date, the results of several scientific studies do not support the claims that these materials are effective repellents for mosquitoes or other biting insects, mites or ticks.

Repellent Plants
In recent years, plants such as Citrosa have been promoted as having mosquito repellent properties. These plants contain many of the same chemicals found in oil of citronella. However, results of scientific studies of these plants have not supported the claims of effective mosquito-repellency in outdoor areas.

Electronic pest repellers
A variety of battery powered ultrasonic pest repelling devices (e.g., flea/tick collars, hanging or pocket devices for mosquitoes) can be purchased from retail outlets or mail order companies. Manufacturers allege that the high frequency sound emitted by these devices "repel" mosquitoes, ticks, fleas and even cockroaches. Scientific tests of these devices do not indicate that they repel or reduce the attack of biting insects, ticks or mites, nor do they eliminate cockroach infestations.