The bug spray ingredient known as DEET is the product most recommended for protection against West Nile virus, and it is toxic to infants. DEET is also harmful to adults if used improperly.
DEET (N,N-diethyl-m-toluamide) is the active ingredient in insect repellents that works to repel the mosquitoes that can carry the West Nile virus. Because DEET is absorbed through the skin, and because infants’ skin is so thin, DEET should never be used on an infant, or children younger than two months old.
Pharmacologist M.B. Abou-Donia, who is a professor of pharmacology, cancer biology, and neurobiology at Duke University, explains on the Duke Medicine Web site, that the warning has to do with metabolism. Once the infant absorbs the DEET chemical, she will not be able to metabolize the drugs as well as an adult.
Professor Abou-Donia also recommends that adults avoid combining DEET with other medications, including over-the-counter antihistamines. He explains that antihistamines, and possibly other drugs as well, can combine with DEET to cause toxic, long-term side effects. When DEET is used for short-term limited exposure times and label directions are followed, toxic effects are minimized. However, Abou-Donia warns against using high-concentration products that contain more than 30 percent DEET.
The professor also cautions in other sources against using DEET in combination with other pesticides such as permethrins, which are often the active ingredient of other brands of bug repellant. DEET also has a synergistic effect with isopropyl alcohol, ethyl alcohol, and freon, which can be present in some commercial formulations of DEET, especially sprays.
The most effective, most recommended protection available against West Nile virus, the insect repellant, DEET, is toxic to infants and adults if used incorrectly. DEET has been available on the market for consumers to use since 1957. While the substance is toxic, it is also highly regulated and warnings about its toxicity and recommended use appear on the product labels.
When choosing to use DEET, consumers must follow the label directions precisely to avoid adverse effects. According the NIH and NLM, there are harmful effects from breathing in or swallowing the bug spray. The side effects of swallowing DEET would include stomach irritation, nausea and vomiting with low blood pressure and heart rate.
Recognizing the side of too much DEET on the skin is important as well: Rashes, hives, and irritation may indicate a reaction at lower doses, while blistering, scarring and mood swings with insomnia indicate the effects of higher doses. Neurological damage is the most serious side effect from being in contact with too much DEET internally or externally, and is experienced as disorientation, clumsiness, and seizures or coma. Infants and small children who are in contact with too much DEET on their skin will experience seizures.
Another consideration when using DEET is selecting the correct concentration. The concentration of DEET in a product may range from less than 10 percent to well over 30 percent. Products with concentrations around 10 percent are effective for periods of approximately two hours. As the concentration of DEET increases, the duration of protection increases, so the temptation is to use more, however the higher concentrations constitute a larger exposure to the toxin.
As public health officials continue to identify cases of West Nile virus in humans, they will continue to advise the public to protect themselves against mosquito bites by using insect repellent, among other strategies. Officials can ensure that the protection they recommend does not lead to unintended consequences by providing the key information that DEET is toxic to infants and should not be used on children younger than two months old.
By Lane Therrell
Duke Medicine News and Communications
North Carolina Department of Health & Human Services