Lauren Manaker, MS, RDN, LDN, CLEC, CPT, has studied nutrition for almost two decades. She was named an emerging leader in women's health by the National Academy of Nutrition and Dietetics.
Nick Blackmer is a librarian, fact-checker, and researcher with more than 20 years’ experience in consumer-oriented health and wellness content.
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TikTok has brought us some unique health-related content—remember Nyquil-marinated chicken and Pink Sauce? With cold and flu season upon us, the “immune-boosting” tips are making the rounds on social media.
Along with the classic advice to get plenty of vitamin C and wash your hands often, there’s a new suggestion trending on TikTok: onion water.
The first recommendation for onion water (that is, water that’s been infused with raw, chopped onion) was made by @earthenchild on TikTok. The claim is that drinking onion water can fight RSV, flu, sinus infections, coughs, and colds. Since that video was posted, people have been sharing their versions of the tonic and toting its benefits.
As you’d probably expect, onion water is no miracle cure during cold and flu season. But are there any risks to drinking onion water? Here’s what experts say.
Before we look at whether water infused with raw onion could be a “cure” for anything, let’s consider what we know about the health benefits of onions when they’re part of our diets.
Roxana Ehshani, MS, RDN, CSSD, LDN, a board-certified sports dietitian, told Verywell that onions on their own are quite nutrient-dense, containing vitamins, minerals, antioxidants, and 25 different flavonoids.
Specifically, one raw red onion contains about:
“Onions have been used for their culinary and medicinal properties for centuries,” William Li, MD, a physician and author of Eat to Beat Disease, told Verywell. “They contain a natural bioactive called quercetin that has anti-inflammatory properties.”
Some research has suggested that the anti-inflammatory effects may support immune system function.
Onions also contain selenium, which Stella Bard, MD, a Texas-based rheumatologist, told Verywell can help “decrease inflammation and help initiate the immune response.” Bard added that the veggie also contains soluble fiber. Fiber supports a healthy gut microbiome, which in turn, promotes healthy immune function.
On their own, onions won’t meet 100% of your daily need for vitamin C (the star of immune system support), but they will give you some. When they’re part of a balanced, nutrient-dense diet, onions could certainly help support a strong immune system.
Eating onions is one thing. But can drinking water that’s been infused with onion offer the same benefits as including them in your diet?
“Adding onions to water—such as the demo on TikTok—will not release much of the quercetin into the water,” Li said.
By not eating the fiber of the onion, you’re missing out on the prebiotic fiber that is naturally found in a whole onion. These prebiotic fibers help support healthy and diverse gut microbiota.
The benefit of onion water is mostly the water, which provides hydration.
Since 70%-80% of immune cells are present in the gut, research suggests that there’s a direct relationship between the gut microbiota and the mucosal immune system.
Not getting these prebiotics means not getting the gut health support that may, in turn, support certain aspects of immune health. Plus, it’s unclear how many of the immune health-supporting micronutrients would be present in the water once you drink it.
“There is no evidence that drinking onion water can increase immune function that leads to faster clearance of colds or the flu—both of which are caused by viruses,” Li said. “The benefit of onion water is mostly the water, which provides hydration.”
Drinking onion water may sound like a low-risk remedy to explore—especially if you would prefer a more natural approach to cold and flu prevention. That said, there are some words of caution to consider before trying it.
Many fruits and vegetables can become contaminated with bacteria like salmonella or listeria. You can get really sick if you ingest these organisms.
Back in the summer of 2022, the TikTok trend of submerging avocados in water to extend their shelf life triggered a warning from the Food and Drug Administration (FDA).
There are also health risks of combining fresh produce and water—especially if the concoction is unrefrigerated.
Onions have been recalled due to salmonella or listeria contamination in the past. Submerging them in water for an extended time could carry a similar risk that soaking avocados did—especially if the onion was not washed thoroughly and the water is not refrigerated during the infusion process.
Bard also cautioned that onion water could cause irritation in some people when ingested thanks to sulfur-containing compounds that are naturally found in the vegetable.
Drinking onion water is not going to keep you from getting sick this winter. In fact, it could even raise your risk for foodborne illness. At the very least, the drink could be irritating and unpleasant. Luckily, there are plenty of other evidence-backed (and better-tasting) ways to give your immune system a boost.
United States Department of Agriculture. FoodData Central: red onion, raw.
Li Y, Yao J, Han C, et al. Quercetin, Inflammation and Immunity. Nutrients. 2016;8(3):167. doi:10.3390/nu8030167
Wiertsema SP, van Bergenhenegouwen J, Garssen J, Knippels LMJ. The interplay between the gut microbiome and the immune system in the context of infectious diseases throughout life and the role of nutrition in optimizing treatment strategies. Nutrients. 2021;13(3):886. doi:10.3390/nu13030886
North Carolina State University. Infused water safety tips.
Food and Drug Administration. Investigation Report: Factors potentially contributing to the contamination of red onions implicated in the summer 2020 outbreak of Salmonella Newport.
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