Today I read a tweet from @Funny_Truth:

Tweet image

"Don't wet your toothbrush after you put toothpaste. Water will reduce the healthy benefits of toothpaste."

Is it true? If it is what does actually happen?

  • 2
    Given that saliva is 99.5% water it seems unlikely that a little more water would have a detrimental effect.
    – Johnny
    Commented Nov 21, 2014 at 18:47
  • I'll admit that I always assumed that the water had less to do with the toothpaste and more with softening bristles stiffened with leftover toothpaste from the last time so that you're not scratching up your gums. Commented Nov 24, 2014 at 20:02

1 Answer 1


No, water actually improves the positive effects of brushing your teeth.

The water activates and solubilizes the non-ionic surfactants and detergents in the toothpaste. These both cleanse the mouth, fight bacteria, and enable more even spread of the paste through the oral cavity.


The water mixes with the abrasives in the toothpaste and softens their cutting power. This lets them still attack plaque while not scouring your teeth.

As seen here.

  • 1
    Thanks for your answer. I have taken the liberty to add a one-line summary. Also, while the reddit answer is detailed and looks convincing, it does not quote any sources. It would be great if you could find some official recommendations or actual studies to support your answer.
    – P_S
    Commented Nov 21, 2014 at 10:22
  • 7
    Welcome to Skeptics!. This answer is an appeal to an anonymous authority. It may be right, but we have no way of knowing whether it is from this answer.
    – Oddthinking
    Commented Nov 21, 2014 at 11:15

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