I have been researching this product.  The serious adverse reactions are seizures.  I have learned of three of my extended family that have experienced this in their fur babies.  I am not sure if it is something in my line that has this reaction but I encourage you to NOT use this product.  There are many other products that are safer.  I personally use a natural product called Wondercide Spot On.  I don't sale this product nor do I get a kick back, I just always try to use natural products because chemicals are extremely harmful.