Insect repellent

Description
Insect repellent is used to keep biting insects such as mosquitoes, biting flies, ticks, chiggers and fleas away from your skin and clothing. Insect repellent can also help protect you from exposure to diseases carried by these insects.
How it works
DEET (N, N-diethylmetatoluamide) is a common ingredient in insect repellents that deters insects from biting your skin. In fact, DEET is the most common repellent used in the United States. DEET blocks insects' receptors, preventing them from being attracted to the odors, moisture, warmth and carbon dioxide humans produce.

DEET, which is registered with the Environmental Protection Agency (EPA), has been proved to be the most effective repellent for preventing diseases transmitted by insects. Most commercial insect repellents -- including liquids, lotions, gels, towelettes and aerosol sprays -- contain DEET. Other repellents such as citronella and eucalyptus may also be helpful in deterring insects.

Concentration
Depending on the product, concentrations of DEET range from 4 to 100 percent. Products containing higher concentrations of DEET generally provide longer-lasting protection. This protection seems to peak at concentrations of about 30 to 50 percent. Higher concentrations are sometimes used in special situations, such as in areas where there's a high risk of infection transmitted through biting insects. Extended-release formulas reduce the concentration while extending the duration of protection. Most of the commercial products available contain 40 percent or less DEET.

The best approach is to use the lowest concentration of DEET effective for the amount of time spent outside:

30-percent DEET protects for six hours
24-percent protects for five hours
20-percent protects for four hours
6.65-percent protects for two hours
4.75-percent protects for an hour and a half
Generally, DEET should not be applied more than once a day. However, if you are outside for a longer than expected time and are being bitten, you can reapply repellent. Also, sweating, perspiration or getting wet may require reapplying repellent, but do so only if you're being bitten.

Using DEET on top of already applied sunscreen may reduce the effectiveness of both products as well as increase skin absorption of the chemicals in the products. There are newer combination products, OFF! Skintastic with Sunscreen, for example, with SPF 30 and 10-percent DEET, but reapplying this type of product often (as is encouraged with many sunscreen products) could expose you or your child to too much DEET.


DEET and young children
Even for children, DEET-containing products are the most effective insect repellents. The safety of DEET does not appear to be related to the concentration in the repellent. There are no studies on skin absorption of DEET in children, but studies of similar substances suggest that absorption through the skin would not differ after 2 months of age. Currently, 30 percent DEET is the maximum concentration recommended for infants and children over 2 months of age. Again, the concentration of DEET used is based on the time the child is expected to be outside. Keep insect repellent out of reach of children at all times.

General use and precautions
When applying insect repellent containing DEET, follow the directions on the product label. If you're using a topical (applied to the skin) prescription medication, check with your doctor before using DEET. Also, keep the following guidelines in mind for you and your child:
Only apply the repellent to exposed areas of the skin, using as little as possible. Heavy applications do not provide increased protection. Apply sparingly to exposed skin folds, and do not apply under clothing. Do not use products containing DEET under diapers or in areas of skin-to-skin contact, such as the groin area, the front of the elbows or the backs of the knees. Using DEET in these areas may cause the skin to become red, painful or blistered.

Don't inhale or ingest DEET products, don't spray in enclosed areas, and don't use near food. Wash your hands before eating.

Use caution when applying the repellent to your face. Keep the product out of your eyes, nose and mouth area. Do not spray aerosol products directly onto your face. Instead, spray the repellent on your hands and gently apply it to your face.

Do not allow children to touch products containing DEET or apply insect repellent by themselves. Avoid DEET products on children's hands as they often have a tendency to put their hands in their eyes and mouths. Discourage children from licking areas of their skin treated with DEET.

Do not apply products containing DEET to injured, irritated or sunburned skin. This increases the risk of absorption through the skin.

Avoid repeated applications of DEET products. If continuous protection is needed, alternate with a product containing an active ingredient other than DEET.

Read product labels before applying anything containing DEET to surfaces such as fabrics or upholstery. DEET does not typically damage natural fibers, but it may harm leather, synthetics, plastics, eyeglass frames, watch crystals, and painted or varnished surfaces (including automobiles).

Follow fire safety measures if the product contains alcohol, which is flammable.

When protection is no longer needed, remove the product from your skin with soap and water. Do the same for any children who have insect repellent on their skin. Wash any clothing that has been sprayed with DEET before wearing again.

Adverse reactions
Any reactions to DEET are typically minor, such as tingling, mild irritation or sloughing (the peeling of dead skin) after repeated use. For skin irritation after exposure to DEET, wash the affected area several times with generous amounts of soap and water. If the irritation continues, consult your doctor.
DEET has also been known to cause contact dermatitis (skin inflammation and irritation due to contact with an irritating substance) and aggravate existing skin conditions. Use DEET with extreme caution if you have acne, psoriasis (a chronic skin disease marked by patches of raised red bumps covered with white, flaking scales on the scalp, knees, elbows and buttocks), sensitive skin or a history of skin irritation.

Reactions that require medical attention
Although it's not corrosive, DEET is very irritating to the eyes. If your eyes are exposed to DEET, flush them with lukewarm water for at least 15 minutes, then contact your local poison control center or your doctor for further evaluation.

Rarely, DEET can cause more serious reactions, especially if the product is inhaled, absorbed through exposure to the eyes, ingested (especially by a young child) or not used according to manufacturer instructions. Seek medical attention if you or someone you know develops:

hives, swelling, itching, numbness or tingling of the skin, a burning sensation after application, skin blisters or rash, or other signs of an allergic reaction
fast, irregular or troubled breathing, shortness of breath, wheezing or tightness in the chest
unusual weakness
clumsiness or unsteadiness
seizures, tremors or uncontrolled jerking movements
muscle cramps
mental changes or confusion
swelling of the eyelids or around the eyes
slow heartbeat
slurred speech
insomnia
loss of consciousness
coma
Rarely, toxic reactions can be fatal (after ingesting large doses of DEET or other drugs simultaneously, for example). Using syrup of ipecac or otherwise inducing vomiting is typically not recommended for someone who has ingested DEET. Because seizures or coma may develop within 30 to 60 minutes after ingestion, the situation is considered a medical emergency. Contact 911 or your local poison control center immediately if you or someone you know has ingested DEET.

Remember, toxic reactions are more likely when label instructions are not followed, such as swallowing, using over broken skin, and using for days in a row without washing off the repellent in between applications.


Non-DEET insect repellents
When considering a non-DEET insect repellent, check the label to be sure the EPA has approved the product and carefully follow the label instructions.
Citronella oil, a nontoxic substance approved by the EPA, is extracted from the plant Cymbopogon nardus and is often found in "natural" repellents. The protection from citronella oil does not last as long as DEET (usually less than two hours), and more frequent applications are typically needed. Citronella candles and incense may also help repel insects.

Numerous plant oils, including allspice, basil, cedar, cinnamon, garlic, geranium, lavender, verbena, peppermint, pine, rosemary and thyme, have been reported to have repellent activity. Although most preliminary tests have demonstrated protection that lasts from a few minutes to two hours, the true effectiveness of these plant oils has not been established.

Research done with Skin-So-Soft bath oil has found that this product does not provide very effective protection from mosquitoes (10 minutes). A recent study of a new product, Skin-So-Soft Bug Guard Plus, demonstrated protection for about 20 minutes.

That same study found a natural repellent marketed as "Blocker" provided protection for about an hour and a half. This repellent is a combination of soybean oil, geranium oil and coconut oil.

A new botanical product containing eucalyptus oil, marketed under two names, Repel Lemon Eucalyptus Insect Repellent Lotion and Fite Bite plant-based insect repellent, was tested in the same study and was found to provide protection for an hour and a half.

A number of pills, including vitamin B1 and garlic, have also been reported to repel insects. However, research has not yet shown any oral repellent to be effective.

Permethrin is an EPA-approved insecticide that works to kill insects rather than repel them. Permethrin is not applied to the skin. Instead, it's applied to clothing, tents and mosquito nets to kill ticks, mosquitoes, flies, chiggers and other insects. Permethrin retains its effectiveness for up to two weeks, despite as many as five launderings. The risk of adverse effects is low because the skin does not readily absorb permethrin.

Considerations
Keep your local poison control center or emergency services phone number available in case of accidental poisoning or ingestion.

Pregnancy-specific information
If you're pregnant, limit your exposure to areas known to be heavily infested with insects. Although there have not been any adverse effects reported in pregnant or breastfeeding women who used insect repellent, check with your doctor before using any medications or products such as insect repellents while you're pregnant or breastfeeding.

Senior-specific information
Your immune system may become less effective as you get older. Review with your doctor your current medication use and the potential interactions of DEET, especially if you take multiple medications or have allergies. Take the same precautions listed above when there's a risk of exposure to insect bites. Ask your doctor about special considerations if you have a chronic illness or other medical concerns.

Prevention of insect bites
In addition to insect repellents, consider the following suggestions to deter insects outdoors:
Avoid scented products such as perfume, soap, lotion, aftershave. Also avoid scented hair spray and deodorant.

If you must be in a wooded area, avoid ticks by walking on the center of trails, and avoid grassy and marshy areas.

To avoid bees and wasps, be extra cautious around flowers, gardens, fruit trees, food and garbage areas. To minimize the risk of ingesting a venomous insect, keep all beverages covered. As another general precaution, don't leave any beverages unattended -- especially soda and beer cans.

Wear loosely fitting clothing that covers as much of your body as possible, preferably including long sleeves and pants. To avoid bees and other venomous insects, don't wear bright colors, especially yellow and white, or floral-patterned clothing. Light-colored clothing is best in tick-infested areas because you may be more likely to spot a tick before it attaches to your skin. Always tuck the bottoms of your pant legs into your socks. Don't forget to wear shoes, but avoid sandals or shoes with open toes or heels.

If possible, stay indoors or in screened-in areas when insects are present. To avoid mosquitoes, for example, be careful during the evening and night.

After outdoor activities, do a complete body, scalp and clothing check for ticks and other insects. Pets should also be examined before they come inside.

Empty any containers of standing water to avoid breeding mosquitoes. Keep wading pools and other containers turned over when not in use. Change the water in birdbaths at least every three to four days. Keep your roof gutters cleaned and draining properly.

Consider contacting your local mosquito control program for assistance or questions regarding control of mosquito populations, especially if treatment of ponds and other wet lands may be necessary.