Neurological , Psychological, and Dermal Effects of DEET pesticide use, Review

New studies have confirmed the case that commonly used mosquito and tick control pesticide, DEET, has neurotoxic effects, especially in combination with other pesticides and chemicals found to have synergistic effects (1). Some types of mosquitos have been found to become resistant to the effects of DEET(1b).

Several deaths have been reported related to DEET use. Two deaths were reported in adults following dermal exposure to DEET (Bell et al. 2002). The remaining three cases were all female children, with ages of 17 months, 5 years, and 6 years (Zadikoff 1979; Osimitz and Murphy 1997)[ab]. All three children had been described as having "heavy, "frequent" or "nightly" applications of DEET.

Dermal application in humans of insect repellents containing Deet can produce a variety of skin reactions in humans. Cases of localized skin irritation, large painful blisters and permanent scarring of skin at the crease of the elbow have been reported in soldiers who applied solutions of 50 or 75 percent Deet (Reuveni and Yagupsky, 1982). Results from questionnaire surveys conducted by the National Institute for Occupational Safety and Health (NIOSH) among Everglades National Park Employees indicated a variety of dermal reactions including rashes, irritation of skin and mucous membranes, and numb or burning sensations of the lips among park workers who were highly exposed to Deet-containing repellents (McConnell et al., 1986). Urticaria or dermatitis, resulting from topical Deet exposure has been noted in both children and adults (Maibach and Johnson, 1975; Mayenburg and Rakoski, 1983; Miller, 1982; Oransky et al., 1989; Roland et al., 1985). In one instance involving only limited Deet exposure, the urticaria was accompanied by an anaphylactic reaction (Miller, 1982) (3)

Controlled human exposure studies using 50 or 75 percent Deet have reproduced many of the dermal effects noted in field studies . The U.S. Army conducted an investigation in volunteers using 75 percent Deet applied to the upper arm and elbow's crease. Of the 77 volunteers, 37 (48%) had severe dermal reactions at the crease of the elbow. No dermal reactions were observed on the upper arm or in the control group of men tested with ethanol solvent alone (3).

Several cases of toxic encephalopathy associated with the use of Deet in children have been reported in the medical literature. The first reported case involved a 3.5 year old girl whose body, bedclothes and bedding were sprayed each night for two weeks with an insect repellent containing 15 percent Deet (3). Since then, five additional cases of toxic encephalopathy have been temporally associated with the use of Deet products in children, all of whom were females (Edwards and Johnson, 1987; de Garbino et al., 1983; Heick et al., 1980; Roland et al., 1985; Zadikoff, 1979). The toxic encephalopathy was characterized by agitation, weakness, disorientation, ataxia, seizures, coma and in three cases resulted in death. Autopsies conducted on two fatalities (Heick et al., 1980; Zadikoff, 1979) indicated edema of the brain, with one case presenting necrotic lesions in the cerebellum and spinal cord and an enlarged liver accompanied by microscopic changes (Heick et al., 1980). One child was reported to be heterozygous for ornithine carbamoyl transferase deficiency (a sex linked enzyme deficiency which may produce effects similar to those reported above) and it has been hypothesized that children with this enzyme disorder may be at greater risk of adverse reactions to Deet (Heick et al., 1980). This enzyme deficiency which usually causes infant death in males is of variable severity in females (Stanbury et al., 1983). Accidental and deliberate ingestion of Deet-containing products has produced neurotoxic effects similar to those described following dermal exposure (Tenenbein 1987, Zadikoff, 1979) (3)

Generalized seizures have also been temporally associated with the use of Deet-containing insect repellent on skin (Oransky et al 1989). These cases differ from those described above in that they involved males (four boys aged 3-7 years and one 29-year-old adult), had few associated neurotoxic effects and resolved rapidly. Lower exposure to Deet in these males (four of five males had either one or two dermal applications) may have accounted for the effects being less severe than in females. That the majority of identified neurotoxic cases involved children raises concerns that this subpopulation is at greater risk of adverse reaction following exposure to Deet than are adults [b].

Signs and symptoms of more subtle neurotoxicity have also been associated with extensive dermal application of Deet in adults. Questionnaire results indicate that Everglades National Park employees having extensive Deet exposure were more likely to have insomnia, mood disturbances and impaired cognitive function than were lesser exposed co-workers (McConnell et al., 1986). A young male who repeatedly applied Deet to his skin prior to spending prolonged periods in a sauna was reported to develop acute manic psychosis characterized by aggressive behavior, delusions and hyperactivity (Snyder et al., 1986) (3).

A case of dermal DEET exposure resulting in psychological effects involve males 27 and 30 years old. In one case the 27-year-old applied Deep Woods Off! (20% DEET) while fishing on a humid afternoon. The man experienced an altered mental state and paresthesias, which progressed to auditory hallucinations and severe agitation. He was heavily sedated when he arrived at the hospital and required mechanical ventilation. After 24 hours, his condition had improved and he was discharged after 3 days with no recurring symptoms (Hampers et al. 1999).(2)

Exposures of Military Personnel-Dermal Effects

Unique cutaneous side effects have been reported in fewer than 15 soldiers who applied military-issued DEET repellents. A 19-year-old soldier applied a 33% DEET repellent to his skin, and then slept with the repellent still on his skin. He developed a vesiculobullous eruption of his left antecubital fossa, which cleared after 14 days (McKinlay et al. 1998). A 20-year-old soldier noticed a burning sensation and skin eruption in his antecubital fossa area after sleeping with repellent on his skin for 8 hours. The man was treated with corticosteroids for 10 days, and the lesions disappeared without sequelae (Amichai et al. 1994). Reuveni and Yagupsky (1982) reported an additional 10 soldiers who developed a burning sensation and erythema in the antecubital fossa after applying a 50% DEET solution before sleeping. Four of the soldiers were referred to a dermatologist, and only three soldiers received medical treatment. In two of the soldiers, a permanent scar remained in the location of the erythema. Once of the cases required corrective surgery after scar tissue formation.

In a controlled test following the initial reactions, 63 soldiers volunteered for testing. They were treated with a gauze pad soaked in DEET that was applied to the antecubital fossa. Of the 63 soldiers tested, 46% of them developed a reaction to the treatment. The reactions varied in intensity, but all had epidermal changes. However, when the men were also patch-tested on their upper arms in a similar manner, none had a reaction, suggesting that the antecubital fossa was uniquely sensitive to the irritant effects of DEET. A second control group was tested at the U.S. Naval Hospital in Oakland, CA to confirm DEET as the cause of the symptoms, and the results were consistent with the cases that occurred in Vietnam (Lamberg and Mulrennan 1969). These cases would suggest that it is prudent to wash DEET from the skin surface before sleeping. (2)

DEET (N,N-Diethyl-meta-toluamide)
Chemical Technical Summary for Public Health
and Public Safety Professionals

Results of a case-control study in Sweden on subjects between the ages of 30-75 with testicular cancer were evaluated for possible risk involving occupational exposures. Those who were exposed to insect repellents containing DEET for intervals <115 days and >115 days made up two exposure groups. These groups were evaluated by multivariate analysis of exposure. A conditional odds ratio (OR) and 95% confidence interval (CI) were used. An increased risk for testicular cancer was found for those who were exposed to insect repellents, with an OR of 2.3 (95 CI 1.2-4-4) for those exposed for =115 days (n=24 cases). The OR for those exposed <115 days (n=15 cases) was 1.2 (95% CI 0.6-2.5) (Hardell et al. 1998). These data do not necessarily suggest that long-term use of DEET could cause testicular cancer. DEET was not the only chemical substance that the volunteers were exposed to, and the authors of the study note that their findings should be "...interpreted with caution and might be chance findings. Some numbers were based on low numbers of exposed subjects" (Hardell et al.1998). (2)

1. (a) Vincent Corbel, Maria Stankiewicz, Cedric Pennetier, Didier Fournier, Jure Stojan, Emmanuelle Girard, Mitko Dimitrov, Jordi Molgo, Jean Marc Hougard and Bruno Lapied. Evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent deet. BMC Biology, Aug 2009; & (b) N. M. Stanczyk, J. F. Y. Brookfield, R. Ignell, J. G. Logan, L. M. Field. Behavioral insensitivity to DEET in Aedes aegypti is a genetically determined trait residing in changes in sensillum function. Proceedings of the National Academy of Sciences, 2010; & (c ) http://www.naturalnews.com/029136_deet_toxic.html

2. ATSDR, Health Effects in Humans, Agency for Toxic Substances and Disease Registry
Atlanta, Georgia, www.atsdr.cdc.gov/consultations/deet/health-effects.html

3. DEET Information Profile, Extension Toxicology Network, http://pmep.cce.cornell.edu/profiles/extoxnet/carbaryl-dicrotophos/deet-ext.html