evidence: Putting a raw onion inside a sock and sleeping with it overnight is a remedy that some people believe can treat a cold or the flu. However, more scientific research into this is necessary. [...] Before scientists identified germs as being responsible for illness, people believed that raw onions could purify the air in the room. When placed against the skin of the foot and kept in a sock, people thought that onion could cleanse the blood. People claimed this purification process could cure the common cold or the flu. [...] Although raw onions are not proven to cure a cold when put against the soles of the feet, onions do have some health benefits when eaten. They are a low-calorie, high-fiber, high-nutrient food and contain vitamin C. Eating onions may: