I had to whisk Kizzy to the vet late this afternoon. I gave her Stronghold spot on on Sunday, yesterday I saw a small "bald" patch, but this afternoon I noticed the place was much enlarged and slightly inflamed, so I phoned the vet and got an appointment.
She has some cream x 2 per day for 5 days which should at the very least stop any irritation and discomfort. The vet said that reaction to Stronghold is very rare.
Poor little Kizzy - she was so good at the vet and allowed the cream to be put on. Luckily, it's in a place not easily reached by her sweet little tongue.
I'll let you know how she gets on.