Activity of repellents applied to skin for protection against Amblyomma americanum and Ixodes scapularis ticks (Acari: Ixodidae).

Twenty-nine repellents were tested on human skin for duration of activity as protectants against nymphal lone star ticks (Amblyomma americanum) and against black-legged or deer ticks (Ixodes scapularis Say). Eleven of these repellents, including deet, provided > 2 h of protection against the lone star tick. One repellent, 1-(3-cyclohexenyl-ylcarbonyl) piperidine, was effective > or = 4 h. Four repellents (2 pyridines and 2 piperidines with protection lasting 2.3-3 h) showed acaricidal activity to more than half of the ticks tested after 9-12 min of exposure. Seven repellents that were most effective against A. americanum, including deet, were tested against the black-legged tick. None was effective and no knock-down was observed. These results suggest that the black-legged tick is less sensitive to repellents than the lone star tick.