Hello Dipa Thank you for using HCM and shared your query with us, I think probably you have a medical condition like iron deficiency anemia because one of the symptoms is unusual cravings for non-nutritive substances in your case to eat slate pencil, I advice you go to the doctor for a physical exam and some lab tests, just in case that nothing else is wrong, you need to stop that bad habit because your body does not have the natural ways to eliminate the toxic and this is accumulating in your organs as a result you can get a chronic disease or allergic process in a long period of time. I hope that my advice has been helpful, take care