The hair of 300 horses belonging to short hair and long hair races had been routinely treated during the last 3 years with a neem seed extract (MiteStop®) in order to kill mallophages (e.g., specimens of the genus Werneckiella). It was found that in all cases, a hidden infestation with these biting lice had existed, which became visible when the product (diluted 1:20 with tap water) was brushed onto the hair. The mallophages left the body surface and became visible as a fine "wooly looking" layer at the tips of the hair. Furthermore, this treatment stopped the forming of dandruff of the skin of the horses, which, in case of heavy mallophage infestations, had looked like being powdered. Another interesting result of the treatment was reported by the riders. They described that the product had a considerable repellent effect on bloodsucking tabanids, mosquitoes, ceratopogonids, simuliids, as well as on licking flies. This repellency effect was noted to last for up to 7 days if the horses were not washed.