I used Hartz flea collars on all 4 of my cats who are all under a year old. After about an hour of wearing the flea collars my cats began to act different. Usually my cats will eat anything you put in front of them, but all of a sudden they wouldn’t eat any of their treats or chicken I had for them. They were also acting very sluggish and lethargic. I assumed that they may just not be fond of having to wear collars. The next night one of my cats Darwin began crying and I had no idea why. I followed him into the bathroom where I saw him vomiting a weird yellowish green liquid that was sort of frothy and there was also a bit of diarrhea on the floor. I took the collars off each cat after this happened. But, now I’m really not sure what to do and I am not sure if my cat is going to be alright. Darwin seems more relaxed now, he is laying down in the bathroom. Is there ANYTHING to fix this or am I too late?