Are Onions High in Histamine? Exploring the Antihistamine Properties

November 18, 2025 •

3 min read

According to numerous food sensitivity and health resources, fresh onions are generally considered to be low in histamine and may even possess natural anti-histamine properties due to their quercetin content. This may come as a surprise to those seeking to manage histamine intolerance, but it is important to understand the nuance behind this common kitchen staple.

Quick Summary

Fresh onions are typically low in histamine and may provide anti-histamine benefits from the flavonoid quercetin, making them suitable for most individuals on a low histamine diet. Factors like freshness, preparation, and individual sensitivities can affect tolerance, so monitoring your body's response is key.

Key Points

Low Histamine Content: Fresh onions, including red, white, and yellow varieties, are generally low in histamine and suitable for most low-histamine diets.
Natural Antihistamine: Onions are a rich source of the flavonoid quercetin, a potent natural antihistamine and anti-inflammatory compound.
Freshness Matters: Histamine levels can increase in food over time, so consuming fresh onions is preferable to ensure a lower histamine load.
Cooking Considerations: While cooking may slightly affect histamine content, fresh, boiled, or lightly cooked onions are generally well-tolerated by those with sensitivities.
Individual Variation: Personal tolerance for onions can differ, and monitoring your body's response is the most reliable way to determine if they are right for your diet.
Managing Overall Load: Onions are safe for most, but the focus should be on managing the total histamine intake from all foods, rather than singling out this low-risk vegetable.

Understanding Histamine and Histamine Intolerance

Histamine is a chemical involved in the immune response, digestion, and nerve signaling. In healthy individuals, an enzyme called diamine oxidase (DAO) effectively breaks down excess histamine. Histamine intolerance occurs when there is an imbalance between the body's histamine load and its ability to degrade it, leading to a build-up that can cause various symptoms. These can include headaches, digestive issues, hives, and nasal congestion. While many foods contain histamine, most foods on a low-histamine diet are fermented or aged.

The Truth About Onions and Histamine

Counterintuitively, onions are not typically considered a high-histamine food. In fact, they contain a high concentration of the flavonoid quercetin, a powerful natural antihistamine. Quercetin helps to stabilize mast cells, which are responsible for releasing histamine, thereby reducing the body's overall histamine load. This is particularly true for red onions, which contain a high concentration of this beneficial compound. Fresh onions, regardless of the variety, are often included on lists of low-histamine foods.

Factors Affecting Onion Tolerance

While onions are generally considered low in histamine, individual tolerance can vary significantly. Several factors can influence how a person with histamine intolerance reacts to them:

Freshness: Histamine content can increase as food ages. Fresher onions are more likely to have lower histamine levels than older ones. It is best to consume them soon after purchasing or store them properly.
Preparation: Cooking methods can also impact histamine content. Boiling or simmering onions for extended periods may cause histamine to leach into the cooking liquid. However, some cooked preparations may be better tolerated than raw for some individuals.
Other Ingredients: The total histamine load of a meal is important. A dish with onions might also contain other ingredients that are high in histamine, such as tomatoes or aged cheese, which could be the source of symptoms.
Individual Sensitivity: Some people with histamine intolerance or a true onion allergy may react to even trace amounts. It is crucial to monitor your body's specific response rather than relying solely on general guidelines.

Cooking and Incorporating Onions into a Low-Histamine Diet

Including onions in a low-histamine diet requires some careful consideration to maximize their benefits and minimize potential reactions. The preparation method and the freshness of the ingredient are key to success.

Use Fresh Onions: Always opt for the freshest onions possible and use them shortly after purchase. The longer an onion is stored, the more its histamine content can rise.
Boiling or Simmering: If you are particularly sensitive, boiling or simmering onions may be a gentler cooking method. This can help to reduce the levels of biogenic amines, including histamine, that are present.
Eat Raw or Lightly Cooked: To preserve the maximum amount of quercetin, consuming red onions raw or lightly cooked is recommended. For individuals with a higher tolerance, this can be the most beneficial approach.
Combine with Low-Histamine Foods: Integrate onions into meals composed of other low-histamine ingredients. This helps control the overall histamine load and makes it easier to pinpoint the source of a reaction if one occurs.

Comparison Table: Onions vs. High-Histamine Foods

This table provides a simple comparison to illustrate why onions are typically included in low-histamine diets, contrasting them with common high-histamine culprits.


Food Item	Histamine Level	Reason for Rating
Fresh Onions (All varieties)	Low	Not a significant source of histamine; contain anti-histamine compounds like quercetin.
Aged Cheeses (Parmesan, Cheddar)	High	The aging and fermentation process increases histamine content.
Fermented Foods (Sauerkraut, Kimchi)	High	The fermentation process involves bacterial action that produces histamine.
Processed Meats (Sausage, Cured)	High	Curing and processing methods lead to higher histamine accumulation.
Tomatoes	Histamine Liberator	Can trigger the release of the body's natural histamine, though not always high in histamine itself.
Spinach	Histamine Liberator	Also known to trigger histamine release in some sensitive individuals.

Conclusion

In summary, fresh onions are not high in histamine and are generally considered a safe and beneficial addition to a low-histamine diet. Their rich quercetin content provides natural anti-histamine and anti-inflammatory benefits that can be helpful for managing histamine-related symptoms. However, individuals with histamine intolerance should always prioritize listening to their body, considering factors like freshness and preparation methods, and working with a healthcare professional to create a personalized dietary plan. The key is to manage the overall dietary histamine load, and in this context, onions prove to be a helpful ally rather than a foe.

Frequently Asked Questions

Yes, generally all fresh types of onions, including red, white, and yellow, are considered low in histamine. Red onions are particularly noted for their high quercetin content, which has natural anti-histamine properties.

Cooking can potentially reduce the histamine content of onions, particularly methods like boiling. However, the effect is often minor, and fresh onions are generally low enough in histamine not to pose a problem for most with histamine intolerance.

Yes, it is possible to have an onion allergy, which is an immune system response, rather than a histamine intolerance. In this rare case, your body would release its own histamine in response to the onion, potentially causing severe symptoms.

Quercetin is a powerful flavonoid found in high concentrations in red onions. It is known to have natural anti-histamine properties by helping to stabilize mast cells, which reduces the release of the body's natural histamine.

Reactions to onions among individuals with histamine intolerance can stem from various factors, including individual sensitivities, the freshness of the onion, and the presence of other high-histamine foods in the same meal. Some people may also be sensitive to other compounds in onions.

Both raw and cooked onions are typically fine for a low-histamine diet, with personal tolerance being the most important factor. To maximize the beneficial quercetin, raw or lightly cooked red onions are recommended, while those who are very sensitive might tolerate boiled onions better.

Dehydrated onions are not considered significantly high in histamine, as the dehydration process does not significantly alter the histamine content. However, as with fresh onions, individual tolerance should be monitored.