Losing fur after flea treatment

Yesterday morning I applied Advantage flea control for cats over 9 pounds to my cat. It was her first treatment of the year. However, in past years I've applied Advantage to her, but splitting a tube between her and my other cat, and she's always been fine. Now as she is over 9 pounds my vet recommended I apply one whole tube on her.

Today I noticed she's losing a ton of fur, and I realized it's because she is scratching at the spot on her neck where I applied the flea treatment. The fur flies off when she scratches there, and the spot will soon be bare.

As far as I know, I applied the treatment correctly, although I do think a small amount may have dripped onto the fur because of the position of her head. Still, it seems she's having some kind of reaction to the treatment, perhaps because it was too strong a dose for her. Has anyone else had this happen to their cat? Should I take her to the vet, or will she be fine? Should I try and wipe the irritated spot with a bathing cloth? Thanks for any advice.

Call your vet, or if they're closed call any vet around that is open.
I don't know if thats a really bad reaction or just a slightly bad reaction. Its def. not normal though!

If you are positive it is the same area as the Advantage and cannot get into see a vet I would wash it with a mild shampoo and rinse it really, really well with coolish water. In allergic reactions to topically applied products a cool rinse helps close the pores in the skin and limits absorption.
If he continues to go at it a cat sized dose of benadryl couldn't hurt.

I am not a vet and this is just anecdotal information, but I have experienced a dog allergic to Frontline and this is how my vet said to treat it.

Our cat had a similar problem with Frontline. The vet thought that it was a minor allergic reaction. He seemed to think that it was because Puppy had never been on the medication before, so his skin wasn't used to it. He suggested we continue for a few months and see what happened. It happened the next month, but not since.

If it's not too bad, he might get used to it. Call your vet to be sure though.