Insect agents safe, effective as directed

June 1, 2007

Several insect repellents are available for use in the United States. A review of published information confirms they are effective and have low toxicity when properly used. Ongoing research may lead to new products working via an alternate mechanism of action that could be sprayed into the air rather than applied directly onto the skin or clothing.

Key Points

Houston - Findings of a review of published information on insect repellents reinforce the conclusion that currently available agents are very safe when used as directed and highly effective for protecting against annoying or possibly harmful insect bites, say researchers from the University of Texas Health Science.

"False impressions about the potential toxicity of insect repellents appear to be relatively common, particularly regarding DEET and especially with respect to use in children.

"Our research indicates that, when used properly, DEET and other insect repellents are extremely safe and provide effective protection against bug bites that can cause significant morbidity and even serious, life-threatening infectious diseases," says Tracy Katz, B.A., a fourth-year medical student at the University of Texas Houston Health Science Center where she will be starting an internal medicine internship in July 2007. Her research on insect repellents was done in collaboration with Adelaide A. Hebert, M.D., professor and director of pediatric dermatology, and Jason H. Miller, M.D., dermatology resident.

DEET details

DEET provides broad-spectrum protection against ticks, mosquitoes and other arthropods when applied to the skin or clothing.

It is found in a large number of marketed products at concentrations ranging from 5 percent to 100 percent. DEET products have a concentration between 10 percent and 30 percent and have been recommended by the American Academy of Pediatrics Committee on Environmental Health as acceptable for use in children over 2 months of age.

"The duration of activity of DEET increases with increasing concentration, but it reaches a plateau of about six to eight hours at 50 percent. Most DEET products contain less than 40 percent of this active ingredient," Ms. Katz notes.

Adverse events

Adverse events associated with DEET include skin and allergic reactions, as well as serious neurological reactions, cardiovascular events and even fatalities.

However, overuse or misuse is a common theme in cases of serious adverse events.

"A review of reports of DEET-related toxicity reveals there are even cases involving intentional ingestion, and, in pediatric cases, there is evidence the insect repellent was used incorrectly in almost every situation. Failing to follow the instructions for proper use increases the risk for side effects," Ms. Katz says.

"When applying insect repellents in children, parents are cautioned to avoid spraying the face directly and to avoid applying the product to unexposed skin; skin around the eyes, mouth, hands; or in areas where there are cuts or irritation. In addition, the insect repellent should be washed off with soap and water after coming indoors."

Picaridin particulars

There is less information published about picaridin, but it ms to have a lot of attractive features that bring it closer to matching the criteria for the "ideal" insect repellent.

"Picaridin has low toxicity and irritant potential and has some cosmetic advantages relative to DEET, as it is not greasy or sticky when applied to the skin, is odorless and does not damage clothing," Ms. Katz tells Dermatology Times.

Picaridin has been widely used in Europe and Australia but was only approved as an insect repellent in the United States in 2005. It is available in this country in two formulations - a pump spray containing 7 percent active ingredient (Cutter Advanced) and an aerosol spray with 15 percent picaridin (Cutter Advanced Sport).

Picaridin appears to be comparable or even superior to DEET for repelling mosquitoes, although there is minimal direct comparative data available.

"Based on its efficacy and safety profile, the World Health Organization in 2000 recommended picaridin was the insect repellent of choice for use in areas where there are malaria-carrying mosquitoes," Ms. Katz says.

Picaridin products are also labeled for protection against ticks. They are not recommended for use in children under 2 years old.

Botanicals

Botanicals used as insect repellents include oil of lemon eucalyptus, soybean oil and geraniol.