Insect repellents and contact urticaria: differential response to DEET and picaridin

Topical insect repellent is commonly used throughout the world. Active ingredients typically include N,N-diethyl-meta-toluamide (DEET) or picaridin. Reactions to topical repellents have ranged from contact dermatitis to urticaria. Exposure to DEET can produce contact urticaria; however, it is unknown if patients with a sensitivity to DEET can tolerate picaridin. We report the case of a 22-year-old man who presented for evaluation of contact urticaria that had developed immediately after the application of insect repellent and contact with individuals who had used DEET-containing repellents. No systemic manifestations were noted. Commercially available products containing DEET or picaridin were used for open patch testing. The patient showed immediate urticarial responses to 7% DEET and 7% DEET in ethanol, but patch tests for 5% picaridin and 5% picaridin in ethanol were negative. Based on these results, we conclude that insect repellents containing picaridin may be acceptable alternatives in patients who demonstrate sensitivity to products containing DEET.