[ladyjane]

I agree, I would follow my instincts and opt for a different preventive. I personally like Heartgard for heartworms ... and used to use Advantage for fleas. Fortunately I never have issues with fleas and have not used anything in a few years.

I would not use Trifexis or Comfortis.

My vet recommends Nexguard now, but I read it can cause vomiting and diarrhea. You really should speak with your vet about options and try it for one month to see if it is the Sentinel. Sentinel can cause vomiting and diarrhea! They say it is rare, but that means it is highly possible that is the problem.