Dr. Aanchal Panth I Dermatologist on Instagram: "Comment “Iron” to know how to test and for other symptoms of deficiency . Pica is the persistent eating of non-food, non-nutritive substances (like chalk, clay, ice, paper, soil, hair). It can occur in children, pregnant women, and adults, and usually points to an underlying issue. Here are the main reasons: Iron deficiency is the most common cause for pica and ruling it out is important. Here are the reasons for Pica : 1. Nutritional deficiencies