Most of us grew up using foaming toothpaste. The chemical in toothpaste that causes foaming is sodium lauryl sulfate (SLS), a surfactant with a rather significant down side, including interference with taste buds. This makes foods taste more bitter and, of course, encourages consumption of more pleasant tasting food. There are some more serious issues with SLS, including increasing susceptibility to allergies or aggravating existing allergies and possibly promoting canker sores in some users. This ingredient does not perform any useful functions so it should be considered am aesthetic choice with a troubling potential for problems. Getting used to non-foaming toothpaste is a challenge, but anyone with oral sores should definitely consider the shift as should those who are trying to remineralize their teeth because the SLS tends not to leave the teeth fully exposed to saliva, think of it as soap that was not sufficiently removed.
A lot of effort has been made to find the safest toothpastes possible. Those who are highly sensitive will probably be surprised to find that peelu does an incredibly good job without a long list of ingredients.