My baby's heart seems to be beating awfully fast. See also My baby's heart seems to be beating awfully fast. Over the first several years of his life, it will gradually slow down.
Some medications can make the heart race, including decongestants in allergy and cold medications.
If you've given your baby one of these products and you find that his heart is racing, call your pediatrician immediately. It's not common, but medications that stimulate the heart can trigger an abnormal heart rhythm if a child is prone to them. Minor variations in heart rate and rhythm are fairly common in babies, and they're usually harmless. Just to be safe, though, you might mention it at your baby's next checkup. Add your comments to the bottom of this page.