Does anyone know of an over the counter antihistimine or medicine to give to a dog for allergies, and how much do you give for different size dogs. thanks

Benadryl works quite well. I'm not a Vet so I cant say what dose to give.
I have giveing 1/2 a tablet twice a day and didn't kill my dog.

I like the red liquid benadryl 1cc for above a 10# pup is my gess shampoo