In general, it's safe to eat raw potatoes, but it isn't recommended. Uncooked potatoes do have the potential to be harmful.
Most of the toxic substances produced by potato plants are contained in the leaves and stems rather than in the part of the potato that grows underground that is consumed by humans. However, according to horticulturists at Purdue University, once potatoes have been harvested and exposed to sunlight, they may produce green patches on their skin that contain chlorophyll. Although chlorophyll isn't harmful, it is a sign that photosynthesis has occurred.
Another product of photosynthesis is solanine, a toxic alkaloid that is extremely harmful if eaten. For this reason, it is not safe to eat potato sprouts or potatoes with green spots on them. Unlike other harmful substances, including salmonella and e.coli, solanine is not destroyed by cooking.