evidence: Verywell / Laura Porter Onions As Prevention: Origins of the Remedy The onion cold remedy, which involves placing sliced onion in the bottom of your socks while asleep, has origins in both medieval healing and traditional Chinese medicine (TCM). Medieval Origins The idea that onions can prevent transmittable diseases dates back to the 1500s, according to the National Onion Association. During the bubonic plague, cut onions were placed around homes to keep people from contracting the deadly illness. At the time, it was believed that all illnesses were spread through the air as clouds of disease known as miasma (derived from the ancient Greek word for "pollution"). Miasma was meant to be something you could smell, and onions, with their distinctive smell, were thought to literally absorb miasma and provide protection. In medieval Italy, the concept of miasma even gave rise to the term malaria, literally translated as "bad air." In more recent history, people used onions in a room to provide protection against the 1918 Spanish flu pandemic. In one anecdote, a doctor was said to have ordered his patients to place cut onions in their homes, which he claimed kept them healthy while others around them did not.