Tickless Hunter Ultrasonic Tick Repellent Environmentally friendly contains no chemicals or fragrances. Tickless Human is the ideal solution to keep ticks away during outdoor activities like hiking, gardening, hunting, walking or camping. Simply attach the device to your clothing, and it will keep ticks away for up to 3,000 hours, allowing your whole family to enjoy nature without worry. (Approx. up to 2 years) It is non-toxic and does not use or release any chemical substances or odors, safe to use for everybody. The device emits ultrasonic pulses that are imperceptible to humans or animals, but interfere with the ability of ticks to orient themselves, thus keeping them away.