My child puts everything in their mouth. Until when? Should I stop it?

For a baby, the mouth is the most sensitive "tool for exploration," and it's natural to have a period of checking things by putting them in the mouth. For children who develop more slowly, this period can last longer. Rather than forcibly taking things away, hand them a toy that's safe to mouth while increasing play they can explore by touch with their hands, and it will naturally decrease. Just be thorough about managing choking-size items (roughly 39 mm in diameter or smaller).