Hello,I would love to help I just have a few additional questions. After your reply please allow a few minutes for me to type your answer.
What brand was this and for what size dog?
Is either cat having any facial twitching or muscle tremors?
Did you apply the drops to the head?
Thank you for the additional information.
You want to use full strength dish soap to wash off the flea prevention. Weakened will not allow it to remove the oils.
In the future you want to apply the drops to the back of the neck and not the head.
You also want to avoid all hartz, zodiac, and sergeants products as they have the highest rate of reactions. These are currently under investigation by the EPA due to the number of reactions including death especially in cats.
If you get this off then most cats will recover in a day or two, Some do require supportive care. I would keep an eye on them for the next day or two. If they stop eating , have any muscle tremors, facial twitching or seizure activity I would have them seen by your vet.
I hope all goes well, please reply back if you have additional questions or concerns