Protection against Mosquitoes and Other Arthropods

Repellents

Travellers should be advised that permethrin-containing repellents (e.g., Permanone) are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered by the U.S. Environmental Protection Agency for this use. Permethrin is highly effective both as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. There appears to be little potential for toxicity from permethrin-treated clothing. The insecticide should be reapplied after every five washings.

The U.S. Environmental Protection Agency has registered several active ingredients for use in personal repellents applied to skin. EPA registration of repellent active ingredients indicates the materials have been reviewed and approved for efficacy and human safety if applied according to the instructions on the label. These active ingredients are DEET (N,N-diethylmetatoluamide), Picaridin (KBR 3023), MGK-326, MGK-264, IR 3535, oil of citronella, and p-Menthane 3,8-diole (Oil of Lemon Eucalyptus).

All the EPA-registered active ingredients have some repellent activity, but most authorities recommend repellents containing DEET (N,N-diethylmetatoluamide) as the most reliable and long-lasting. DEET repels mosquitoes, ticks, and other arthropods when applied to the skin or clothing. In general, the more DEET a repellent contains, the longer time it can protect against mosquito bites. However, there appears to be no added benefit of concentrations >50%. A microencapsulated, sustained-release formulation can have a longer period of activity than liquid formulations at the same concentrations. Length of protection also varies with ambient temperature, amount of perspiration, any water exposure, abrasive removal, and other factors. DEET-based repellents applied according to label instructions may be used with sunscreen with no reduction in repellent activity.

No definitive studies have been published about what concentration of DEET is safe for children. No serious illness has been reported from use of DEET according the manufacturer's recommendations. DEET formulations as high as 50% are recommended for both adults and children >2 months of age. Lower concentrations are not as long lasting, offering short-term protection only and necessitating more frequent reapplication. Repellent products that do not contain DEET are not likely to offer the same degree of protection from mosquito bites as products containing DEET. Other types of repellents have not necessarily been as thoroughly studied as DEET and may not be safer for use on children. Parents should choose the type and concentration of repellent to be used by taking into account the amount of time that a child will be outdoors, exposure to mosquitoes, and the risk of mosquito-transmitted disease in the area. The recommendations for DEET use in pregnant women do not differ from those for nonpregnant adults.

DEET is toxic when ingested and may cause skin irritation in sensitive persons. High concentrations applied to the skin can cause blistering. However, because DEET is so widely used, a great deal of testing has been done, and over the long history of DEET use, very few confirmed incidents of toxic reactions to DEET have occurred when the product is used properly.

Travellers should be advised that the possibility of adverse reactions to DEET will be minimized if they take the following precautions:

• 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 spray aerosol or pump products in enclosed areas; do not inhale the aerosol.
• Do not apply aerosol or pump products directly to the face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.
• When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid the child's eyes and mouth and apply sparingly around the ears.
• Do not apply repellent to children's hands. (Children tend to put their hands in their mouths.)
• Do not allow children <10 years old to apply insect repellent to themselves; have an adult do it for them. Keep repellents out of reach of children.
• Protect infants 2 months of age by using a carrier draped with mosquito netting with an elastic edge for a tight fit.
• Bed nets, repellents containing DEET, and permethrin should be purchased before travelling and can be found in hardware, camping, sporting goods, and military surplus stores. Overseas, permethrin or a similar insecticide, deltamethrin, may be purchased to treat bed nets and clothes.