I've never used Advantage Plus. So not sure about the product. I think Advantage is safe. I used to use it to rabbits and cats. vet said it's safe. Frontline Plus can kill cats if they lick it. The Plus part is a bit worry. I think you should check on vet about the product.

 

I use Revolution now. It seems to be safe. I usually put it under collars to discourage to lick it directly. My cats hardly lick each others anymore. They are keeping distance. But they used to when they were younger and they are still alive. They might start snuggling up together when weather gets cold.