That would all depend on the size of your child and the age at which he or she has fully developed motor skills and hand-eye coordination. The best way children begin to learn is through imitation, so simply allow your child to witness some of your own hygiene habits as a beginning. As time progresses, show them how to do this on their own. As always, strong encouragement is suggested. Each child initiates and progresses at their own rate, but this can start as early as 24 months.