My dog had a reaction to the shampoo at the groomer's and she got a terrible hot spot on her tail. She's chewed off most of her hair and it is bleeding. The vet gave me a spray and some antibiotics and she told me to give her Benadryl too so that she wouldn't itch so much. I took her to the vet yesterday, but now I can't remember the dosage of Benadryl to give her. I gave her two tablets this morning. She weighs 74 lbs. and is 12 years old. She's a collie/golden retriever mix, if that makes a difference. Should I give her more tonight? Or tomorrow morning? Thanks for your help!