Onions have a range of health benefits when eaten. Onions are a root vegetable and a part of the “Allium” family of flowering plants. Onions are rich in vitamins B and C, potassium, and fiber. 

Onions also contain antioxidants and compounds that, when eaten, help to work against inflammation, decrease triglycerides (a type of fat found in the blood that can be harmful) and lower cholesterol levels. All of these benefits could be beneficial to overall health such as leading to a lower heart disease risk. The anti-inflammatory properties of onions could also help lower high blood pressure and protect against blood clots. More studies are ongoing to understand several other health benefits of onions. 

These benefits are backed by science. The claims that either placing raw onions on a part of the body or leaving cut onions out could be beneficial to health are backed by science. 

Research has been done to assess the ancient (primarily Chinese) practice of foot reflexology, which connects to the claim that putting onions on the feet could help relieve illness. A review of foot reflexology studies showed little evidence that foot reflexology is an effective practice for treating most medical conditions. Some research shows that it could actually make some conditions worse. However, the overall quality of research on reflexology is very low overall. 

There is no research that has specifically been done to assess the benefit of putting onions on your feet or anywhere else on your body. Online claims do not reference any scientific studies, just anecdotes. 

There is also no research that specifically proves the claim of onions on feet are wrong, either. However, the reasons that people claim onions in socks work are questionable. Onions are slightly acidic, so they may have antibacterial results if rubbed onto things. However, if used in this way they would be less effective than a chemical antibiotic or bleach. Viruses also require direct contact with a human host to spread. As a result, an onion would have no impact on a virus inside of the body. 

The same logic extends to germs in the air. There is no scientific evidence that an unpeeled onion can absorb germs and protect people in the room from bacteria or viruses.

Claims can be found in both eastern and western societies about the medicinal properties of onions. Some widely circulated claims include putting onions in one's socks to cure flu-like illness and placing cut onions in rooms to absorb toxins. While onions have some known medicinal properties, there is no scientific evidence about the above claims, and these are largely considered to be myths. 

These claims are not new. According to the National Onion Association, the myth that placing cut onions around the house could absorb toxins in the air goes back to the time of the bubonic plague (mid-1300s), far before the concept of germs was known, and when it was believed that diseases were spread through “bad air.”

Many online sources worldwide still claim these to work; however, these are largely anecdotal and have no scientific explanation.