Allergic Reaction to Vectra medicine!

Hello everyone! I'm a new user on this forum! My Yorkie/Mini poodle mix, Lily, had an allergic reaction to the flea and tick medicine Vectra 3D. We took her to the vet and she told us to just give Lily a bath and it should help. I did and it just made it worse. She is so itchy and uncomfortable. Whenever she walks it is ten times worse. I partially think she is overreacting a little bit, she has a history of doing that. All she does is sleep. She eats, drinks, and uses the bathroom so that is reassuring. Has anyone one else had this happen to them? If so what could I do to make her more comfortable? Thanks!

Plus she keeps rolling around on furniture as if she is trying to get it off

I have had dogs with allergies and skin problems. I use the liquid benedryl for children. For that itchy skin giving an oatmeal bath is very soothing and stops the itching. Also Timsin is great for itchy skin if you can find it. It used to be sold in feed stores. Last time I bought some I had to find it on the internet. If you want more info get back to me.