hello and thank you for asking HCM, I understand your concern. This condition is called pica. There are different variations of pica, as it can be from a cultural tradition, acquired taste or a neurological mechanism such as an iron deficiency, or chemical imbalance. This can be very dangerous since it can lead to intoxication in children, which can result in irregularity in physical and mental development. It can also lead to surgical emergencies such as intestinal obstruction as well as not so urgent symptoms such as nutritional deficiencies. Pica has been linked to mental disorders. There is no single test that confirms pica.Your sisters have anemia which occurs often in pica. The treatment of pica depents on the cause. If iron defficiency is the reason than taking iron supplements can lead to improvement. For pica that appears to be psychotic etiology, therapy and medication such as SSRIs have been used successfully. However, the use of medication untill all non psychotic reason are excluded is not adviced. So my suggestion is to visit your GP and try with iron supplements. If this won t help than perhaps you should do a much more expanded blood test in which you will test other minerals and vitamins. Perhaps you will need too contact a psychologist at the end. I hope this answer was helpful to you.