Are Onions Anti-Histamine? Exploring the Quercetin Connection

January 1, 2026 •

4 min read

According to a 2022 study, quercetin—a flavonoid found in high concentrations in onions—may act as an antihistamine, effectively reducing allergy symptoms. These versatile vegetables contain compounds that may help stabilize mast cells and inhibit histamine release, offering a natural approach to managing allergic reactions and inflammation.

Quick Summary

This article delves into the science behind how onions, particularly their high quercetin content, can have a natural antihistamine and anti-inflammatory effect. It explores the mechanism of action, comparing it to traditional antihistamines, and provides practical advice on incorporating this potent flavonoid into your diet for potential allergy relief.

Key Points

Quercetin Content: Onions, especially red onions, are a rich source of the flavonoid quercetin, which has natural anti-histamine and anti-inflammatory properties.
Histamine Inhibition: Quercetin works by stabilizing mast cells, preventing them from releasing histamine and other inflammatory compounds that cause allergy symptoms.
Raw is Best: Raw onions contain the highest concentration of quercetin, so consuming them raw in salads or salsas can maximize their potential benefits.
Multi-faceted Benefits: The anti-histamine action is complemented by overall anti-inflammatory and immune-modulating effects of quercetin and other compounds in onions.
Part of a Broader Strategy: Incorporating onions is a complementary approach, not a replacement for traditional allergy treatments, and is best combined with other anti-inflammatory foods.
Not a Cure: While beneficial, dietary changes using onions and other natural sources of quercetin are for symptom management and support, not a cure for allergies.

The Allergic Reaction: Understanding Histamine's Role

An allergic reaction is an immune system overreaction to a harmless substance, such as pollen, pet dander, or dust mites. When the body encounters an allergen, it releases a chemical called histamine, primarily from mast cells. Histamine is a powerful mediator of inflammation and is responsible for many common allergy symptoms, including sneezing, itching, a runny nose, and watery eyes. Traditional antihistamine drugs work by blocking the action of histamine on receptors in the body. However, an increasing number of people are turning to natural alternatives, such as foods containing certain compounds, to help manage their symptoms. This is where the potential anti-histamine properties of onions come into the picture.

The Star Compound: Quercetin

Onions, especially red onions, are an excellent natural source of quercetin. Quercetin is a type of plant-based compound known as a flavonoid, which is recognized for its potent antioxidant and anti-inflammatory properties. Unlike conventional antihistamines that primarily block histamine, quercetin works by a different mechanism.

Key functions of quercetin in inhibiting the allergic response:

Mast cell stabilization: Quercetin has been shown to stabilize mast cells, the immune cells that release histamine during an allergic reaction. By keeping these cells from becoming overactive, quercetin can help prevent the excessive release of histamine and other pro-inflammatory chemicals.
Inhibition of histamine release: Research indicates that quercetin can directly inhibit the release of histamine, along with other inflammatory compounds like leukotrienes and prostaglandins, from mast cells. This action helps to prevent or reduce the intensity of allergic symptoms before they begin.
Anti-inflammatory effects: In addition to its antihistamine-like activity, quercetin has powerful anti-inflammatory effects that can calm the body's overall inflammatory response, which is a major driver of allergic symptoms.
Immune modulation: Quercetin can help balance the immune system's response by influencing the activity of different immune cells, such as T-helper cells (Th1 and Th2). By promoting a more balanced immune response, it can help prevent the overreaction that leads to allergic symptoms.

Raw vs. Cooked Onions: Maximizing Quercetin Intake

When it comes to getting the most quercetin from your onions, preparation matters. While cooking does not completely destroy quercetin, it does reduce its concentration. Raw onions, particularly red onions, have the highest concentration of quercetin.

Comparison of Quercetin Levels in Onions


Type of Onion	Quercetin Content	Best Use for Allergy Relief
Raw Red Onion	Highest concentration	Finely diced in salads, salsas, and guacamole.
Raw White/Yellow Onion	High, but less than red	Adds a sharp flavor to salads and sandwiches.
Cooked Onions	Significantly reduced	While still beneficial, the antihistamine effect is less pronounced.

For optimal benefits, incorporating raw red onions into your diet is recommended. This can be as simple as adding thin slices to salads, sandwiches, or dips.

Practical Ways to Incorporate Onions for Allergy Support

To benefit from the quercetin in onions, consider adding them to your daily meals in various forms:

Salads: Top your salads with finely chopped raw red onion for a flavor boost and a dose of quercetin.
Salsas and Dips: Add raw red or white onions to fresh salsas or guacamole.
Sandwiches and Wraps: Layer thin slices of raw onion for a crispy texture and potent flavor.
Soups and Stews: While cooking reduces the quercetin content, the anti-inflammatory properties of cooked onions are still present. Add them to the base of your soups and stews.
Pickled Onions: Quick-pickled red onions retain some of their quercetin and add a zesty crunch to dishes.

Other Anti-Histamine Foods to Consider

While onions are a great source of natural antihistamine compounds, they are not the only option. Combining them with other quercetin-rich foods and natural anti-inflammatory agents can further support your immune system. Some examples include:

Apples: Particularly with the skin on, apples are another great source of quercetin.
Berries: Blueberries, cranberries, and raspberries contain quercetin and Vitamin C, which can assist in breaking down histamine.
Pineapple: Contains bromelain, an enzyme with anti-inflammatory effects that can help reduce nasal swelling.
Turmeric: The active ingredient, curcumin, has powerful anti-inflammatory properties that can inhibit histamine release.
Vitamin C-rich Foods: Citrus fruits, bell peppers, and broccoli are high in Vitamin C, which can also act as a natural antihistamine.

Conclusion

While onions cannot replace traditional medication for severe allergic reactions, incorporating them into your diet can provide natural support for managing allergy symptoms due to their high quercetin content. This powerful flavonoid acts by stabilizing mast cells and inhibiting the release of histamine and other inflammatory compounds. For maximum benefits, consuming raw red onions is most effective, though cooked onions still offer valuable antioxidant and anti-inflammatory properties. By understanding the role of quercetin and strategically adding onions to your meals alongside other beneficial foods, you can take a proactive approach to supporting your body's immune health during allergy season and beyond.

Resources

To learn more about the science behind natural antihistamines and flavonoids, consult authoritative sources such as university health centers and government health research organizations.

National Institutes of Health (NIH) - Quercetin inhibits transcriptional up-regulation of histamine H1 receptor via suppressing protein kinase C-δ/extracellular signal-regulated kinase/poly(ADP-ribose) polymerase-1 signaling pathway in HeLa cells.

Disclaimer

The information provided in this article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Frequently Asked Questions

Red onions typically contain the highest concentration of quercetin, the flavonoid with natural antihistamine properties. For maximum effect, eating them raw is recommended.

Cooking reduces the quercetin content in onions, but does not completely eliminate it. While raw onions offer the most potent effects, cooked onions still retain beneficial anti-inflammatory properties.

Onions and their quercetin content are a natural, food-based approach to managing allergy symptoms, not a direct replacement for pharmaceutical antihistamines. Their effect is generally milder and should be considered a complementary strategy.

Onions are generally considered low in histamine themselves and their quercetin content may help stabilize mast cells, which could potentially benefit those with histamine intolerance. However, individual tolerance varies.

There is no official guideline, but incorporating onions regularly, perhaps several times a week, into a diet rich in other anti-inflammatory foods can provide ongoing support. Regular consumption is key to building up beneficial compounds.

While quercetin supplements derived from onions exist, they may not offer the full spectrum of benefits found in the whole food. The synergistic effects of whole foods are often more potent. Always consult a doctor before starting any new supplement.

Onions are safe for most people, but a small number of individuals may have a food intolerance or allergy to alliums. As with any food-based remedy, it's important to monitor your body's response.