Quoting JBug's*Mommy:" Any suggestion on how much? She's 15 months and 27lbs. Or do you know how I could calculate how much? THANKS everyone"
I'm asuming you have the liquid, which should be 12.5mg/5ml (5ml is 1 teaspoon). So she would get 1tsp. You really can't OD on benadryl, so don't worry about that, and it is weight based, not age. I would give her 1tsp now, see if it helps, and you can give it every 4hrs or so without any consequences. It might make her sleepy though, that's normal. Other reaction is hyperness though, it's about 50/50 which reaction, if any, she would get.