Below are common medication dosing charts. Tips:
If you know your child's weight, it is better to use their weight to get the dose than the age.
Motrin, Benadryl and Claritin/Zyrtec dosing are only for children 6 months and older.
FYI: Benadryl comes only in "children's" liquid preparation, which is 12.5mg/5ml strength. There is no "infant's benadryl" liquid available.