Long before pharmacies lined city streets, healers across Europe, Asia, and the Americas reached for one of the most common kitchen vegetables to treat coughs, fevers, and chest congestion. Onion tea, made by steeping or simmering sliced onions in water, is one of the oldest documented home remedies in existence. Ancient Egyptians revered the onion as a symbol of eternal life, and medieval European herbalists prescribed onion poultices and broths for respiratory ailments with remarkable consistency. In folk traditions from Eastern Europe to the Andes, onion tea sweetened with honey remains a trusted first response to the common cold even today.
What sets onion tea apart from most herbal teas is its dense concentration of organosulfur compounds, the same volatile molecules that make your eyes water when you slice an onion. These compounds, including allyl propyl disulfide and cepaene, have demonstrated genuine antimicrobial and expectorant properties in laboratory settings. Combined with a powerful load of quercetin, one of the most studied flavonoids in nutritional science, onion tea delivers a brew that is as functional as it is traditional. It is not a delicate floral infusion. It is a bold, warming, slightly sweet and savory remedy that smells like a hearty soup and works like one too.
The beauty of onion tea lies in its accessibility. You do not need a specialty health store or a rare botanical supplier. A single yellow or red onion, some water, and a few minutes on the stove are all you need to produce a cup that has comforted generations of people through winter illness. Whether you are brewing it at the first sign of a scratchy throat or sipping it preventively through cold and flu season, onion tea is a remarkable example of how the most powerful plant medicines are sometimes hiding in plain sight on your kitchen counter.
2
cups
Ingredients
- 1 mediumyellow or red onion, peeled and thinly sliced
- 500 mlfiltered water
- 1 tspraw honey (optional, strongly recommended)
- —fresh lemon juice to taste (optional)
- —a pinch of black pepper (optional, enhances bioavailability)
How to Brew
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- Peel one medium yellow or red onion and slice it thinly into rings or half-moons, aiming for slices about 3 to 4 mm thick. Thinner slices release more surface area and extract faster.
- Place the onion slices into a small saucepan and pour 500 ml of cold filtered water over them. Do not use hot water from the tap, as it can contain more dissolved minerals that interfere with extraction.
- Bring the water to a full boil over medium-high heat, then reduce the heat to low and allow the onion to simmer gently for 15 to 20 minutes. The liquid will deepen in color from clear to warm gold and take on the aroma of sweet, slow-cooked onion.
- Remove from heat and allow to cool for 2 to 3 minutes. Use a fine mesh strainer or cheesecloth to strain the liquid into two mugs, pressing the softened onion slices firmly to extract all remaining liquid.
- Stir in raw honey and a squeeze of fresh lemon juice to taste. Add a pinch of black pepper if desired, as piperine in black pepper may enhance the absorption of quercetin. Serve immediately while hot.
- Peel and thinly slice one medium red onion (red onions are preferred for cold brew as they contain higher anthocyanin levels and produce a more visually appealing rose-tinted liquid). Place the slices in a clean glass jar.
- Pour 500 ml of cold filtered water over the onion slices, ensuring all slices are fully submerged. You can use a small spoon to press them down if needed. Do not add any sweeteners at this stage.
- Cover the jar with a lid or a piece of cheesecloth secured with a rubber band. Leave the jar at room temperature for one hour to allow the initial release of compounds, then transfer it to the refrigerator.
- Allow the onion to cold-steep for a minimum of 8 hours and up to 12 hours. The liquid will turn a soft pink-gold color and develop a mellow, lightly sweet onion flavor that is noticeably less sharp than the hot brew.
- When ready to serve, strain the liquid through a fine mesh strainer into glasses. Add raw honey, a few slices of fresh ginger, or a squeeze of lemon to brighten the flavor. Serve chilled or allow to come to room temperature before drinking.
- Peel and slice one large onion into thin rings. In a glass jar or ceramic bowl, alternate layers of onion slices with generous layers of raw honey, beginning and ending with honey. Use approximately 3 tablespoons of honey per medium onion.
- Cover the layered mixture and allow it to rest at room temperature for 4 to 8 hours, or overnight. The osmotic pressure from the honey will draw the onion juice out of the cells, creating a golden, syrupy liquid at the bottom of the jar. This is your concentrated onion-honey extract.
- To make the decoction tea, transfer the entire contents of the jar, including the softened onion slices, into a small saucepan. Add 400 ml of filtered water and stir to dissolve any remaining honey.
- Heat the mixture over very low heat, maintaining a temperature around 85 to 90°C (185 to 194°F). Do not allow it to reach a rolling boil, as excessive heat can degrade the honey’s beneficial enzymes and some heat-sensitive compounds. Let it simmer gently for 30 minutes.
- Remove from heat and steep for an additional 10 minutes off the burner. Strain through a fine mesh strainer into mugs, pressing the onion firmly. Add fresh lemon juice, a pinch of cinnamon, or a small piece of fresh ginger to taste. Drink warm in 100 ml doses throughout the day for maximum therapeutic effect.
Health Benefits
Quercetin in onion tea has been shown in multiple studies to inhibit the replication of influenza and rhinovirus strains. A 2010 randomized trial published in Phytotherapy Research found that quercetin supplementation significantly reduced cold incidence and duration in athletes under physical stress.
The organosulfur compounds in onion, particularly thiosulfinates and cepaene, help loosen mucus in the airways and stimulate mucociliary clearance. This makes onion tea a traditional and functionally credible remedy for wet coughs, bronchitis, and chest congestion.
Quercetin inhibits the release of pro-inflammatory cytokines including IL-6 and TNF-alpha, which are responsible for the swelling and discomfort associated with sore throats. Drinking warm onion tea coats the throat while delivering these anti-inflammatory compounds directly to irritated tissues.
Both water and ethanol extracts of onion have demonstrated inhibitory activity against Streptococcus mutans, Staphylococcus aureus, and Escherichia coli in laboratory studies. While tea is a more dilute medium than concentrated extracts, the antimicrobial compounds remain bioactive in water-based preparations.
Onions are one of the richest dietary sources of fructooligosaccharides, prebiotic fibers that selectively stimulate Bifidobacterium and Lactobacillus species. Since approximately 70 percent of immune tissue resides in the gut, regularly consuming onion tea may contribute to a more resilient systemic immune response.
🧪 Key Bioactive Compounds
The Science Behind Onion
The therapeutic reputation of onion tea is not merely folkloric. The primary active compound, quercetin, is one of the most extensively studied flavonoids in human nutrition research. It exerts its effects through multiple mechanisms: it acts as a direct antioxidant by neutralizing reactive oxygen species, it inhibits the enzyme cyclooxygenase-2 (COX-2) to reduce prostaglandin-driven inflammation, and it has demonstrated the ability to block viral replication by interfering with the 3C protease enzyme used by rhinoviruses and influenza A strains. Quercetin also acts as a natural zinc ionophore, facilitating the transport of zinc ions across cell membranes into cells, where zinc inhibits RNA polymerase and thereby disrupts viral reproduction. This quercetin-zinc synergy may explain why traditional onion and honey remedies work especially well when paired with zinc-rich foods.
The organosulfur compounds in onion, including allyl propyl disulfide, cepaene, and dipropyl trisulfide, are released in greater quantities when onion cells are disrupted by slicing. In the body, these compounds contribute to onion’s expectorant properties by stimulating secretion from the mucous membranes of the bronchial tree, effectively thinning mucus and making it easier to clear from the airways. Research published in the journal Phytomedicine has confirmed that aqueous onion extracts reduce bronchial hyperreactivity in animal models, providing a mechanistic basis for the traditional use of onion preparations in cough and asthma management. The anti-platelet activity of cepaene, while a consideration for those on blood thinners, also contributes to improved circulation, which can help deliver immune cells more efficiently to sites of infection.
Perhaps the most underappreciated aspect of onion tea’s immunological profile is its prebiotic content. The fructooligosaccharides and inulin-type fructans in onion are water-soluble and partially extracted into the tea liquid during brewing, particularly during longer cold-brew or decoction methods. These prebiotic fibers selectively stimulate growth of beneficial gut bacteria, which in turn produce short-chain fatty acids like butyrate that regulate T-cell differentiation, reduce intestinal permeability, and modulate systemic inflammatory tone. This gut-immune connection means that onion tea may provide immune support not only through its direct antimicrobial and antioxidant compounds but also through promoting a more balanced and resilient microbiome over time.
Brewing Tips
- Use the outer layers of the onion, including the papery skin, when making the hot brew or decoction. Onion skin contains up to 4 times more quercetin per gram than the inner flesh layers. Simply rinse the outer skin well and add it to the simmering pot, then strain it out before drinking.
- Red onions generally contain higher concentrations of quercetin and anthocyanins than white or yellow onions, making them the preferred choice when your primary goal is immune support. Yellow onions, however, tend to produce a milder, more palatable flavor if you are new to onion tea and find the taste challenging.
- Do not discard the softened onion slices after straining. The cooked onion that remains after simmering still contains beneficial fiber and can be mashed with a fork and stirred into soup or eaten on toast with a little olive oil and black pepper, making the entire vegetable useful rather than wasteful.
Great post on quercetin, which research consistently shows can modulate inflammatory responses in respiratory tissue. One thing worth noting: the sulfur compounds in onions (like quercetin’s partner ally, allicin) are fat-soluble, so simmering onions in water captures some benefits, but pairing this tea with a small amount of healthy fat, olive oil or butter, may enhance absorption. I’ve seen patients get better outcomes when they treat onion tea as part of a broader anti-inflammatory approach rather than a standalone fix, but as a food-first intervention it’s hard to beat.
Great point about the fat-soluble compounds, Oliver! I’d add one heads-up for folks with histamine concerns: onions are moderate histamine and do liberate histamine when cooked/fermented, so I’ve found fresh raw onion or very briefly cooked works better for my mast cell activation than a long simmer. For anyone who reacts to onion tea but wants those quercetin benefits, I’ve had success with fresh garlic (lower histamine than aged) blended into bone broth with a splash of olive oil, or even just quercetin-rich foods like fresh apples and berries prepared fresh. Totally agree though that treating it as part of a broader protocol rather
Love the histamine point, Lorraine, that’s practical intel a lot of people miss. From a recovery standpoint, I’m also thinking about the protein synthesis angle here: quercetin’s anti-inflammatory effects can help reduce exercise-induced muscle soreness, but you’d want to pair this tea with actual complete protein (think eggs or Greek yogurt post-workout) to capitalize on that recovery window rather than relying on the tea alone. The synergy matters more than either piece in isolation.