BOSTON – Insect repellents containing DEET or picaridin are safe when used properly, and are important for bite protection in children, according to Mercedes E. Gonzalez, MD.
Insect bite reactions are common in children aged 2-10 years, and the emergence of Zika virus raises new concerns about the dangers of mosquito bites, in particular; the World Health Organization has declared Zika-related effects – namely microcephaly and Guillain-Barré syndrome – to be a “public health emergency of international concern.”
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In children, illness associated with Zika virus is generally mild, but can include fever, rash, conjunctivitis, and/or arthralgia, Dr. Gonzalez said at the American Academy of Dermatology summer meeting.
DEET, used since 1957, is effective against mosquitoes, black flies, ticks, mites, and land leeches. It works by forming a vapor barrier that deters insects from coming into contact with the skin. The barrier extends about 4 cm from the skin. DEET can also be used on clothing but may cause damage to spandex, rayon, acetate, and leather, and can dissolve plastic and vinyl.
Although it is available in concentrations of 5%-100%, concentrations of 10%-35% provide adequate protection in most situations, said Dr. Gonzalez of the University of Miami.
Animal studies using large doses have shown that DEET is not a specific neurotoxin, and while there have been case reports of central nervous system toxicity in humans, there is no link to DEET dose or mechanistic pathway. Reported deaths have involved intentional ingestion and overuse or incorrect use of products, she said.
In fact, safety concerns are so minimal that the Environmental Protection Agency removed labels indicating caution in children, and the American Academy of Pediatrics recommends the use of DEET for preventing insect bites in children older than age 2 months, and in pregnant and lactating women.
One DEET safety concern, however, is flammability. Both DEET and the aerosol vehicle used in some DEET-containing products, are flammable, so caution is warranted, she said. Occlusion following use of DEET should also be avoided as it can increase absorption, and the product should be washed off after use.
Picaridin is another insect repellent that, like DEET, forms a vapor barrier to deter insects from getting close to the skin and biting, and can be used on both the skin and clothing, but it does not damage plastics or fabrics.
It has similar efficacy as DEET, and has a number of advantages over DEET in that it is odorless and does not feel sticky or greasy when applied. It has not been reported to cause any serious toxicity or mutagenesis.
Picaridin – which is effective against mosquitoes, dog and deer ticks, chiggers, and flies – has been used in Australia since 1998, and in the United States since 2005. That year, the Centers for Disease Control and Prevention recommended that it be used to protect against West Nile virus, and the World Health Organization said it was the best agent for preventing malaria, Dr. Gonzalez noted.
“So when [patients] ask about the best insect repellent, for most situations I do recommend DEET or picaridin, at 10%-25% for DEET, or 7%-15% for picaridin,” she said. She encourages people to read labels, noting that the EPA is encouraging the use of “repellency awareness” labels on insect repellents to inform the consumer whether it prevents against mosquitoes and/or ticks, and for how long.
It helps to provide specific recommendations, providing pictures and circling those that are recommended. Selling the products in the office is also a good idea to make sure patients “leave with the right product,” she said.
Also, advise patients about what to avoid, such as products that contain blends of natural plant oils, which have been shown to be ineffective, providing less than an hour of protection, she said.
Dr. Gonzalez also advises against the use of combination insect repellent/sunscreen products. One reason is that sunscreen needs frequent reapplication, while insect repellent does not. Further, studies have demonstrated that using sunscreen over insect repellent dramatically increases the percutaneous absorption of DEET, and reduces the SPF of the sunscreen. If both are needed, sunscreen should be applied first to reduce transdermal penetration of the active insect repellent ingredient, and should be reapplied every 2 hours, she said.
“Proper insect repellent use is just one part of protection,” she added.
Other measures that should be encouraged include the use of protective clothing, such as light cotton long sleeves and pants; avoidance of clothing with bright colors or flowery prints; avoidance of scented soaps, perfumes, or hair spray; removal of mosquito habitats by eliminating any standing water, covering gaps in doors, using screens and nets; and, if possible, staying indoors at sunrise, sunset, and early evening when mosquitoes are most active.