Commercial products are not effective at repelling European deer keds, <i>Lipoptena cervi</i> (Diptera: Hippoboscidae) but may increase mortality after exposure

European deer keds, Lipoptena cervi (Linnaeus, 1758), are hematophagous ectoparasitic flies known to bite cervids and noncervids, including humans. To prevent deer keds from landing and biting hosts, 5 commercially available insect repellents (DEET, IR3535, oil of lemon eucalyptus (OLE), picaridin, and permethrin) and water control were evaluated to determine repellency efficacy and postexposure mortality of deer keds. While there was a significant difference between the groups tested, a post hoc analysis revealed that no treatment was significantly different from the water control. Deer ked survival was different amongst the treatments, with deer keds exposed to permethrin dying much sooner than those exposed to other treatments or control (median survival for permethrin = 0.58 h). Post-hoc pairwise comparisons revealed that deer keds exposed to DEET or IR3535 had similar survival rates (4.82 and 5.15 h, respectively). Still, there were significantly lower survival times for DEET compared to OLE (6.33 h) and picaridin (15.00 h). Deer keds exposed to the water control survived the longest (23.12 h). Overall, deer ked repellency was not significantly different from the control, but permethrin-treated clothes can effectively kill deer keds in a short amount of time, thereby protecting those who recreate outdoors or encounter animals carrying deer keds.