For years, one of our patients vomited every time it rode in a car. Countless cleanups later, we performed a minor surgical procedure on the senior cat that necessitated the placement of an Elizabethan collar. Miraculously, for the first time in its traveling life, the cat did not vomit on the way home, and, still wearing the E-collar, the cat didn't vomit on the way back to the clinic for suture removal. Since then, I have suggested E-collars as a treatment for car sickness for more than a dozen cats and even a couple of dogs, and, anecdotally, it seems to work.
Tom Morganti, DVM