Chewing ice is the body's way of getting a nutrient that has been missing. If chewing ice is persistent, there is a chance the person is anemic and that the habit is caused by an iron deficiency.
Correcting the intake of iron can alleviate the desire for ice; beef, eggs, and shellfish are foods high in iron. The desire to chew ice can also be a form of pica, which is when people desire to eat non-food items with no nutritional value. For others, chewing ice may simply be a habit. Eating ice is not dangerous as long as it is not a replacement for nourishment.