Q: My toddler puts everything in his mouth. He seems to like to feel things with his tongue more than his fingers! Why does he do this and what can I do to get him to stop?

A: If you’re a parent to a young toddler, you can probably easily predict the first place a new toy will end up–in their mouth. At this age, this is the main way toddlers explore the world around them. Although you certainly know this, you may wonder why this is, and why this stage seems to last so long. Interestingly, there is some science behind it.

What scientists say

Although touch is not entirely understood, especially when it comes to the oral senses, scientists have evidence to suggest that the mouth and hands, the two parts of the body toddlers most use to explore their world, are the most sensitive when it comes to touch.

Specifically, research by Kenneth Johnson of Johns Hopkins University shows that “the tongue, lips, and fingertips are the most touch-sensitive parts of the body.”

Similarly, in the Encyclopedia of Neuroscience, it says that “the density of the oral sensory innervation has not been quantitatively estimated, but is thought to be rivaled only by that of the hand.”

Basically, the density of touch receptors present in the fingertips, lips, and tongue can give toddlers the most possible information about the objects they are exploring.

This is reflected in the Encyclopedia of Neuroscience, which says that “the exceptionally high innervation densities of the tips of the tongue support its unique role in manipulation and exploration of objects.” This explains why toddlers and babies can’t seem to stop putting things in their mouths.

So how long does this stage last?

The “mouthing” stage of development starts when infants are able to grasp objects and bring them to their mouths. It happens during the first stage of development, the sensorimotor stage, which starts at birth and lasts until about 2 years.

In this stage, infants and toddlers learn mostly through their senses, thus explaining why they seem obsessed with putting things in their highly sensitive mouths. Luckily this stage doesn’t last forever.

You can expect that your toddler will stop putting things in his mouth around age 2 when he graduates from the sensorimotor stage of development to the preoperational stage. At this point, play begins to focus more on the symbolic meaning of objects rather than their physical properties. If he doesn’t, you might want to have him evaluated for sensory processing disorder.

What to do in the meantime

Even though toddlers eventually stop putting everything in their mouths, in the meantime you can make sure to have a safe environment for them to explore. Keep small choking hazards out of their reach, make sure that cleaning supplies and medicines are safely locked away, and keep toys relatively clean. This can ensure that your toddler can explore their environment safely.

Conclusion

In sum, toddlers put things in their mouths because this is a highly sensitive part of the body, thus providing them with a lot of information about objects in their environment. This stage will last about as long as your toddler is still in the sensorimotor stage of development, in which he primarily learns by exploring the physical properties of objects through his senses.

I should note that toddlers also sometimes put things in their mouth because they are teething. You might want to check out our article on how to deal with teething issues.