This is poisoning from swallowing or eating dirt.
There are no particular poisonous ingredients unless the dirt contains contaminants such as insecticides, herbicides, fertilizers, parasites, and waste.
Callahan GN. Eating dirt. Emerg Infect Dis. 2003;9(8):1016-1021.
Davis S, Mirick DK. Soil ingestion in children and adults in the same family. J Expo Sci Environ Epidemiol. 2006;16(1):63-75.