Toddlers and slightly older children are prone to chew on things that make adults react with alarm. However, for many children between the ages of two and three, compulsively eating non-food items is an eating disorder known as pica. Learn more on this Moment of Science.
Things like coffee grounds and charcoal are called “physical deodorizers,” because they absorb tiny particles in the air that are causing the smell. The problem is, eventually they reach a state called “equilibrium,” in which the deodorizer has absorbed all it can.