The desire to chew on ice is called pagophagia, and if a person has an intense desire to chew ice they of  will often be found to have iron deficiency anemia.

It is the iron deficiency that causes this behavior as the person is seeking iron in their environment, and that desire if focused into eating ice as opposed to other natural substances (such as soil/dirt….non nutritive substances) that have a high level of iron in them naturally.

It is sometimes amazing when I find a person with very low iron levels and anemia and ask them about their ice eating.  They feel like I am a mind-reader.  Often their ice eating, although extreme, has not struck them yet as a bizarre sign that something must be wrong with them.

Pagophagia is just one form of pica, the eating of non-nutritive substances.  Other picas include eating hair, soil, paint chips (thus the children with lead poisoning, and even blood (vampires exhibit pica.)

So….eating ice is fine and is a normal behavior, but if you always feel the need to have ice in an ice chest in your car or cup, you may find that you are anemic and it would be worthwhile getting bloodwork to find out.