For starters, not all toothpaste that winds up on your toothbrush is made up of the same ingredients. One that you'll need to take note of, though, is fluoride. The majority of toothpaste tubes you'll find at the store are formulated with fluoride, which is toxic in large amounts (via Poison Control). Swallowing a bit here and there during normal brushing is no big deal, but if you manage to choke down a big glob on the regular, your stomach might hurt and you could experience diarrhea, nausea, or vomiting.

KidsHealth notes that fluoride poisoning is rare, but that over 80 percent of suspected fluoride overingestion reports are tied to kids under 6, which leaves 20 percent for older kids, and even grownups. No matter how old a person is, a phone call to the poison control center is necessary if it's suspected that someone has ingested too much toothpaste that contains fluoride.