To the best of knowledge of clinical veterinarians consulted who have done research in this area, there is no evidence to verify that what you describe is a true cause-and-effect occurrence. Ivermectin, if it crosses the blood-brain barrier, has not been reported to have any direct effect on mammalian systems other than neurological signs. If hair coat issues are a real result of ivermectin use, it hasn't been proven. We base recommendations on published research, and so far there is none related to ivermectin and hair coats.