Ineffectiveness of ultrasonic flea collars

Ultrasonic flea collars from two companies were evaluated for their ability to reduce flea numbers on cats with experimentally induced flea infestations. Sounds produced by the collars were also evaluated both before and after use to ensure that the flea collars were functional. Each brand of ultrasonic flea collar was evaluated on five cats with each cat being infested with 50 cat fleas (Ctenocephalides felis) for a 7‐day treatment and control period. Cats were declawed and fitted with Elizabethan collars to reduce normal grooming activity. Collars generated 40‐kHz pulses (0.8‐ms exponential rise and fall) every 50 or 20 ms (depending on the device). The level of the stimuli was between 92 and 80 dB SPL at 10 cm and would thus be audible to both cats and dogs. An average of 99.6% and 97.4% of the fleas were still on the cats after treatment and control periods, respectively. The ultrasonic flea collars were totally ineffective at reducing flea numbers on these cats.