UF/IFAS Gopher Service
06/05/95 - DEET MAKING NEWS
TO: County Extension Personnel
FROM: Pesticide Information Office, University of Florida Colleagues,
Recently the media has focused on the insect repellent DEET (N,N-Diethyl-meta-toluamide). The television show Prime Time Live did a piece on DEET on Wednesday, May 31. We are supplying the following information about this product. The source of this information is the University of California, Davis Environmental
Toxicology Newsletter, Number 4, 1989.
In August 1989, epidemiologists from the New York State Department of Health (NYSDH) investigated five reports of generalized seizures temporally associated with topical use of
DEET. Three of the case-patients, one from New York and two from Connecticut, were reported by a pediatric neurologist who practices in both states. One case was reported initially to an entomologist in New York, and one was reported directly to the NYSDH. The cases occurred in June through August 1989.
The patients, four boys aged 3-7 years and one 29-year-old man, had few prodromal symptoms (symptoms which occur before the onset of the seizure) and recovered quickly. All five had unremarkable medical histories, and none had had a previous seizure or neuralgic event. Each had had topical cutaneous exposure to varying concentrations of DEET; four had had fewer than three applications. The interval between last use of DEET and onset of seizures ranged from 8 to 48 hours. One patient developed urticaria (hives) before his seizure; he was one of two patients who developed an urticarial reaction to phenytoin (an anticonvulsant drug) administered to control seizures.
While reinforcing the importance of DEET in preventing Lyme disease (LD [Lyme borreliosis]), health officials in New York, Connecticut, and New Jersey issued a health alert on August 22 advising caution in the use of DEET-containing repellents.
Editorial Note: DEET has been marketed in the United States since 1956 and is used by an estimated 50-100 million persons each year. Since 1961, at least six cases of toxic systemic reactions from repeated cutaneous exposure to DEET have been reported. Six girls, ranging in age from 17 months to 8 years, developed behavioral changes, ataxia (loss of balance), encephalopathy (brain disorder), seizures, and/or coma after repeated cutaneous exposure to DEET; three died. Another six systemic toxic reactions have been reported following ingestion
of DEET. Additionally, episodes of confusion, irritability, and insomnia have been reported by Everglades National Park employees following repeated and prolonged use of DEET.
DEET is partially absorbed through the skin and has been used to enhance dermal delivery of other drugs. Adverse reactions include allergic responses, direct neurotoxicity, and dermatitis (skin rash). One of the girls who died after dermal exposure was partially deficient in the enzyme ornithine carbamoyltransferase; DEET may interfere with the urea cycle metabolic pathway.
Anecdotal reports of seizures are difficult to interpret. None of the recent cases in New York and Connecticut have been clearly established as DEET toxicity. In contrast to cases described in the medical literature, the New York and Connecticut patients were all male, DEET exposure was less intense, few prodromal symptoms or encephalopathy were seen, and recovery was more rapid and complete. With the dramatic increase in the prevalence of DEET use in areas with endemic LD, the reported cases of seizures temporally related to DEET use may be coincidental. However, these cases may represent a different, previously unreported spectrum of toxic reactions. Careful toxicological and epidemiological studies must be conducted, including adequate documentation of DEET levels in affected and unaffected persons. Clinicians evaluating patients with unexplained seizures should consider the possibility of exposure to DEET. However, since the exact circumstances under which DEET-related neurotoxicity may occur are unclear, DEET should not be accepted as the cause of a seizure until appropriate evaluation has reliably excluded other possible etiologies.
The optimal concentration of DEET for
prevention of tick bites is unknown. However, repellents
containing 20%-30% DEET applied to clothing are approximately 90%
effective in preventing tick attachment. To minimize the
possibility of adverse reactions to DEET, the following
precautions are suggested:
- Apply repellent sparingly only to exposed skin or clothing.
- Avoid applying high-concentration products to the skin, particularly of children.
- Do not inhale or ingest repellents or get them into the eyes.
- Wear long sleeves and long pants, when possible, and apply repellent to clothing to reduce exposure to DEET.
- Avoid applying repellents to portions of children's hands that are likely to have contact with eyes or mouth.
- Never use repellents on wounds or irritated skin. Use repellent sparingly; one application will last 4-8 hours.
- Saturation does not increase efficacy.
- Wash repellent-treated skin after coming indoors.
- If a suspected reaction to insect repellents occurs, wash treated skin, and call a physician. Take the repellent can to the physician.
Specific medical information about the active ingredients in insect repellents is available from the National Pesticide Telecommunications Network, telephone (800) 858-7378.
Copyright 1995, University of Florida
