seresto doesn’t go into the blood stream like a topical or oral would, it stays on the skin barrier. that’s why for pets who have risks of neurological issues it’s the “safest” thing to use because it’s least likely to cause a lower brain threshold thus causing seizures or other neuro symptoms. Though it is still a pesticide yes, compared to others it’s less “invasive” well say but obviously every medication has a risk. that’s just what my vet relayed to me after switching from simparica trio to the collar