001566 - Anaphylaxis to diethyltoluamide (DEET) containing insect repellent

Background:

The increased knowledge of insect-borne diseases has led to the development of repellents aimed at preventing transmission. Diethyltoluamide (DEET) has become well-regarded for its effectiveness and is the primary active ingredient in many topical insect repellents. While there have been reports of contact and generalized urticaria associated with DEET-containing products, severe allergic reactions, including anaphylaxis, are rare.

Case Report:

We present the case of a 15-year-old child with a medical history of allergic rhinoconjunctivitis, asthma, and sensitization to house dust mites and dogs.

In 2018, he applied a body and legs insect repellent (DEET 45%, Ethanol 49.9%). Within minutes, he experienced diffuse pruritus, generalized urticaria, and angioedema of his eyelids. He later developed skin paleness, dyspnea, and dizziness. In the emergency department, he was found to have tachycardia and a blood pressure of 100/60 mm Hg. He was treated with intramuscular dexchlorpheniramine (5 mg) and intramuscular epinephrine (0.15 mg). His symptoms gradually improved, and he was subsequently well. Serum tryptase was not measured during the reaction.

In the following months, the patient tried using a different repellent with DEET and sprayed only a small area, which resulted in pruritus and local urticaria without systemic symptoms.

Results:

The study was based on a high suspicion of causality for the repellent solution applied to the skin. An open patch test was performed using the DEET-containing insect repellent implicated in the previous reaction, by applying a small drop of the solution on the patient’s forearm. This led to erythema, itch, and small hives that evolved into a large wheal of 6×4 cm within a few minutes. He developed significant pruritus and was treated with oral antihistamine and topical corticosteroid.

The same test had negative results in two atopic controls.

Tolerance to citronella insect repellents was proven.

Conclusions:

Based on the clinical history and allergology study results, the patient was diagnosed with an anaphylactic reaction to DEET contained in an insect-repellent solution.

Written informed consent was obtained from the patient for the publication of this case report.