I have been a vet assistant for 7 years and have seen to many reaction to off brand flea prevention. Today alone, we had two cats from two different owners come in sick. I feel sorry for the owners that thought they were helping their pet by trying to rid them of fleas. Many owners do not know the dangers of Hartz and other brands of flea control until it is too late. You would think that if they can sell it then it would HAVE to be safe. However, it is not considered a drug it is a pesticide so it is not monitored under the FDA. The worst part is that while trying to save the live of one cat, the fleas are alive and well. I wish that there were more that could be done to get these poisons off the shelves. I would like to note that Frontline and advantage are safe. Unfortuneitly more expensive but safe. BUT DO NOT USE ADVANTICKS ON CATS. It does say not to use it on cats on the box but the box looks alot like Advantage and may be picked up by mistake.