4 min read
mosquito

With summer heat and mosquito activity peaking, it is a good time for a refresher on ways to prevent mosquito bites.

Mosquitos can survive both indoors and outdoors and will bite both during the day and at night. While all mosquitoes bite humans, female mosquitoes bite because they must have blood-meal to produce eggs. These bites can be more than just itchy and annoying. Mosquitoes can transmit diseases that are harmful to humans and can even lead to death.

Prevention

The most effective way to avoid getting sick from mosquito-vectored diseases, both at home and while traveling, is to prevent mosquito bites. The primary prevention methods recommended by the Centers for Disease Control and Prevention (CDC) include the following:

  1. Cover up by wearing protective clothing, like long-sleeved shirts and long pants.
  2. Avoid high-arthropod areas.
  3. Keep mosquitos outside.
  4. Use EPA-approved mosquito repellent products.

Insect Repellent Products

Several new insect repellent products have recently appeared on the market. The are now six effective, EPA-approved insect repellent chemicals recommended by the CDC for skin application as personal protectants against mosquitoes. When a repellent product has an EPA registration, it means that the product have been evaluated and approved for human safety and effectiveness when applied according to label instructions.

Note: The CDC does not recommend use of any type of insect repellent on babies less than two months old.

The six CDC recommended mosquito repellents belong to two general categories: synthetic chemicals and plant-based products in the form of plant extracts, typically plant-derived essential oils. The latter are also known as botanical or herbal products.

DEET was the first synthetic-chemical repellent recommended by the CDC for skin application. It is sold under several different names, with products containing anywhere from five to 80 percent DEET. Products containing more than 50 percent DEET do not offer a marked increase in protection time against mosquitoes but may cause safety concerns. A good rule of thumb is to apply DEET at approximately 25 to 30 percent concentrations, and then reapply as needed. DEET works better at higher air temperatures but can lose its effectiveness because of perspiration or rain.

The American Academy of Pediatricians advises against use of DEET products on infants less than two months old. DEET is a chemical and must be used with caution. It also has an unpleasant odor and some people may not like the feel of DEET on the skin. It has tendency to dissolve plastics (e.g., eye-glass frames, watch crystals) and certain synthetic fibers. Although relatively few cases have been documented, the concern is that DEET is readily absorbed by the skin and can potentially cause neurologic damage in developing babies and infants.

Synthetic Repellent Chemicals

  • Picaridin was approved by the EPA in 2005 as an alternative to DEET, nearly 20 years after it was first created. Field tests have shown that it is just as effective as DEET at repelling mosquitoes. Among its advantages are its colorlessness and the non-greasy feeling on skin. Unlike DEET, it does not dissolve plastics or other synthetic materials.
  • IR3535 products were registered in 2000. It offers similar protection against most species of mosquitoes without the odor, staining or skin irritation associated with DEET. Some studies show its effectiveness is a little weaker than DEET at the same concentrations.

Plant-Based Repellent Chemicals

  • P-Menthane-3,8-diol (PMD) was registered in 2005. It is colorless with a faint mint odor, and stable in sunlight. Studies show it may provide longer protection than other repellents because of its unique low evaporating rate. It also more effective in repelling certain species of mosquitoes than DEET. PMD is not be confused with oil of lemon eucalyptus (OLE), which contains PMD, but is registered in a different category. CDC cautions users to not use this product on children under three years of age.
  • 2-undecanone is also known as methyl nonyl ketone. It is a colorless oily, plant-based repellent, but usually produced synthetically. It is commonly used in washing and cleaning and personal care products. It is deemed a safe compound with weak repellent efficacy.

There are also quite a few natural products that have been used as mosquito repellents. The oil of lemon eucalyptus (OLE), hydrogenated catmint oil (HCO), and oil of citronella (OC) are just three of the numerous plants or plant-based products approved as insect repellent by EPA. They can be found in products that have been registered with EPA or in unregistered products that meet the requirements for exemption from registration.

Which repellents work best to stop mosquitoes from biting?

Repellents with any of the active ingredients approved by the EPA are recommended as safe and effective by the CDC. The differences in duration of protection can be compensated for simply by reapplying the repellent more frequently in the case of the shorter lasting compounds. People should keep in mind that the effectiveness of any repellent is dependent on a number of factors, including the following:

  • different temperatures and environmental conditions
  • different species of mosquitoes
  • individual differences in the relative attractiveness of people to mosquitoes in general

As a result, the choice of a repellent product is a personal matter, taking into account the degree of protection provided, how long it effectively lasts, and individual sensitivities to odor and comfort of the product on one’s skin.

Repellant Effectiveness

The following are tips for using registered skin-applied products:

  • Always follow the product label instruction
  • Reapply insect repellent as directed
    • Do not spray repellent on the skin under clothing, only sparingly apply to exposed skin
    • Never use repellents on wounds or irritated skin
    • Do not inhale or ingest repellents or get them in the eyes
    • Avoid using high-concentration products (>50 percent DEET)
    • If you are also using sunscreen, apply sunscreen first and insect repellent second
    • Always wash repellent-treated skin after coming indoors
  • For children under three years old, do not use products containing OLE or PMD.

 

Featured image by David Cappaert, Bugwood.org.