He was given the Revolution on Monday. I didn't see anything yesterday, but today he has a bald spot where it was applied. He will be going to the vet in 30 days as follow-up because he has roundworms.
As soon as I noticed the spot I put him in the tub and washed the area with his usual cat shampoo, but I'm not sure what good that will do since it has been 3 days since it was applied.
He is otherwise fine, appetite, activity, etc. Do I need to worry about this? Or should I just mention the reaction to the vet in January and see that he gets something different next time?