Do raw onions keep you from getting sick?

January 8, 2026 •

3 min read

A persistent folk remedy suggests that placing raw onions in a room can absorb illness, a myth dating back to the 1500s' miasma theory. The reality is more nuanced: while raw onions do not absorb or prevent viruses this way, their nutritional content can play a supporting role in overall immune health.

Quick Summary

Consuming raw onions contributes to overall immune health through antioxidants and nutrients, but lacks scientific evidence to directly prevent illnesses. They are not a cure.

Key Points

Not a Cure: Despite popular folklore, raw onions cannot directly prevent or cure colds, flu, or other illnesses.
Rich in Antioxidants: Raw onions are an excellent source of the powerful antioxidant quercetin, which has anti-inflammatory and potential antiviral effects.
Supports Immune Function: The high vitamin C content in raw onions helps boost the production of white blood cells, a key part of your body's immune defense.
Enhances Gut Health: The prebiotics found in onions promote a healthy gut microbiome, which is strongly linked to a robust immune system.
Raw vs. Cooked: Raw onions retain more of their beneficial sulfur compounds and vitamin C, but both forms are healthy additions to your diet.
Myth Debunked: The idea that cut onions absorb germs is an old, unscientific folk remedy dating back to miasma theory.

The Myth of Onions and Illness

For centuries, various folk remedies have claimed that raw onions can cure or prevent infectious diseases. One widespread myth, which resurfaces regularly on social media, suggests that placing a freshly cut onion in a room or in a sock can absorb bacteria, viruses, or toxins from the air or body. This belief is not supported by scientific evidence. The idea originated during the bubonic plague when people believed illnesses were spread through "miasma," or bad air. While the strong scent of an onion may make it seem powerful, cold and flu viruses are spread by direct contact, not by floating in the air to be absorbed by a vegetable. In fact, the National Onion Association confirms there is no scientific proof for these claims, stating that the onion's own juices are mildly antimicrobial, meaning they fight bacteria rather than attract it.

The Real Immune-Supporting Power of Raw Onions

While raw onions don't offer a magical cure, they are a nutrient-dense food that can support a healthy immune system as part of a balanced diet. Their benefits are rooted in specific compounds and vitamins, not folklore.

Key Nutrients in Raw Onions

Raw onions are packed with valuable components that contribute to overall wellness:

Vitamin C: An essential nutrient for immune function, vitamin C helps stimulate the production and function of white blood cells, which fight off harmful bacteria and viruses.
Quercetin: Onions, particularly red varieties, are one of the richest dietary sources of this powerful flavonoid antioxidant. Research shows quercetin has anti-inflammatory and potential antiviral properties.
Prebiotics: Onions contain prebiotic fibers like inulin and fructooligosaccharides, which feed beneficial bacteria in the gut. A healthy gut microbiome is directly linked to robust immune function.
Sulfur Compounds: These compounds, which give onions their pungent flavor and aroma, have been studied for their antioxidant and potential antibacterial effects.

Raw vs. Cooked Onions for Immunity

While both raw and cooked onions are healthy, eating them raw maximizes the benefits of certain compounds. Cooking can break down some of the more volatile sulfur compounds and reduce the level of heat-sensitive nutrients like Vitamin C. However, the key takeaway is that both are beneficial. Eating them raw in salads or salsas, or lightly cooking them, provides different but valuable health benefits.

Comparison: Onions vs. Garlic for Immune Support

Both members of the Allium family, onions and garlic are often compared for their health properties. While both are highly nutritious, they offer different strengths for immune support. A key difference lies in their signature compounds and the extent of antibacterial effects.


Feature	Raw Onions	Raw Garlic
Key Compound	Quercetin and sulfur compounds	Allicin and other organosulfur compounds
Immune Mechanism	Antioxidant and anti-inflammatory properties, gut health support	Direct antibacterial and antiviral effects, boosts white blood cell counts
Antibacterial Effect	Moderate; test-tube studies show inhibition of some bacteria	Stronger; allicin is known for potent antibacterial and antiviral action
Best for Immune Support	Broad support through antioxidants, gut health, and Vitamin C	Potent, specific action against certain pathogens
Main Drawback	Digestive discomfort for some individuals	Very strong flavor and odor

Potential Downsides and Considerations

While healthy, raw onions aren't for everyone and should be consumed in moderation. Excessive intake can lead to digestive discomfort such as bloating, gas, and heartburn, especially for those with conditions like IBS. Additionally, onions can have blood-thinning properties, so those on blood-thinning medication should consult a doctor. In extremely rare cases, allergies or intolerances can occur. The risk of bacterial contamination is also higher for raw, improperly stored onions compared to cooked ones.

Conclusion: A Supportive Role, Not a Cure

Ultimately, the idea that raw onions can directly prevent or cure sickness is a myth. They do not absorb or destroy airborne pathogens. However, consuming raw onions as part of a varied, nutrient-rich diet offers genuine health benefits. Their high content of Vitamin C, powerful antioxidants like quercetin, and prebiotics all contribute to a stronger, more resilient immune system. By debunking old myths and focusing on the proven nutritional science, you can make informed choices to support your body's natural defenses effectively. For the most significant health benefits, focus on a well-rounded diet with a variety of fruits and vegetables, and consult a healthcare professional for serious illness concerns.

Frequently Asked Questions

No, this is a folk myth with no scientific basis. Illnesses like colds and flu are spread through direct contact with germs, not by floating in the air for an onion to absorb.

Quercetin is a powerful flavonoid antioxidant found in onions. It helps reduce inflammation, fight oxidative stress, and has shown potential antiviral properties in laboratory studies, though it's not a cure.

Raw onions retain more of their beneficial heat-sensitive compounds like vitamin C and sulfur compounds. However, both raw and cooked onions are healthy and contribute valuable nutrients to your diet.

Yes, test-tube studies show that compounds in onions, including quercetin, can inhibit the growth of certain bacteria. This effect is not potent enough to cure an infection but does contribute to overall health.

For some people, especially those with conditions like IBS, large amounts of raw onion can cause digestive issues such as bloating, gas, and heartburn due to certain carbohydrates (FODMAPs).

Onions are a rich source of prebiotics, which are non-digestible fibers that feed beneficial gut bacteria. A healthy gut microbiome, in turn, plays a crucial role in overall immune function.

There is no official recommendation, and individual tolerance varies. A moderate amount, such as adding slices to a daily salad, is often enough to contribute beneficial nutrients without causing digestive discomfort.