Frontline Reaction?

I gave my cat her second dose of Frontline tonight.   I found fleas on her a month ago and she had the first dose then, she had no reaction.    Tonight, a little while after her second dose, she started making a strange noise like she was trying to clear her throat or something, and I noticed she had saliva strings drooling out of the side of her mouth.  She was agitated and running around for a minute, then she settled down.  Now she seems normal?   Should I be concerned?    I don't believe she got any in her mouth, I applied it where you are supposed to.   Now I don't know what to do.

How is your kitty now?  No further reactions, hopefully?

She's okay, I called the vet and the vet said to keep an eye on her.   That it was possible the frontline burned her or she somehow got some in her mouth which I don't think is the case.   She seemed fine after she first went nuts like that.   Now I don't know what to do.   I don't think she should get another dose next month but I am still seeing the occasional flea drop off of her.