13 month old has a rash on his face. it looks like a heat rash, and he scratches it which makes it worse. he's 34 lbs.

Moisturize, benadryl (diphenhydramine): It is difficult to diagnose a rash without seeing it, but if it itches and is small try some moisturizing cream such as aquaphor or vaseline to keep it from getting too dry. For symptomatic relief you can try 5ml of Benadryl every 6 hours as needed. Here is a dosing table. http://www.stlouischildrens.org/articles/kidcare/diphenhydramine-benadryl-dosage-table.