First-month application I started noticing that Tinkerbell was acting differently. She was very weak and not herself. I thought ok, she is probably having one of her days where she wants to lay around. The other dogs were fine. 2nd-month application, I applied it to all of the little dogs, Tinkerbell did the same then Trixie started acting the same way. I forgot to cancel the 3rd month - in between the 2nd month and 3rd month, Tinkerbell started having seizures constantly. She had 7 within a time frame of 3 hours. They were in clusters. I took her to the vet, and nothing had changed with anything that I had been giving her except this flea and tick application. I to this day feel like this formula harmed Tinkerbell and then I caught it harming Trixie in time to avoid doing any damage to her.