Reduced DEET concentrations may create greater risk for vector-borne diseases

Restricted concentration of N,N-diethyl-m-toluamide, or DEET, in insect repellants could result in increased risk for vector-borne diseases, particularly in European travelers, according to a review published in Parasites & Vectors.

Researchers examined the methods used for determining the safety of DEET in humans, using available literature to compare the toxicity and clinical consequences of the three current models used to create current threshold standards.

Although some people may have significant dermatological reactions to DEET application, others studies found no changes in mortality, body weight, blood chemistry, gross pathology or organ weight at low doses, according to the researchers. Minor adverse reactions were shown only in large-dose animal trials and were not replicated in other test species, according to the review.

Due to the high number of Europeans who travel to regions where vector-borne illnesses are prevalent, the European Union’s 2010 directive limiting the concentration of DEET in insect repellants to 15% or less could result in subtherapeutic activity when the repellants are not frequently applied, according to the researchers.

“The theoretical risks associated with wearing an insect repellant should be weighed against the reduction or prevention of fatal or debilitating diseases, including malaria, dengue, yellow fever and filariasis,” the researchers concluded. “Future European travelers, as a consequence of inadequate personal protection, could potentially be at increased risk of vector-borne diseases.”

Disclosure: Logan is the director and Chen-Hussey is a research scientist at arctec, the Arthropod Control Product Test Centre at the London School of Hygiene & Tropical Medicine, which provides impartial commercial testing services on insect repellent efficacy.