Quercetin side effects: What wellness influencers don’t tell you

Few compounds have attracted as much interest as quercetin in a society fascinated by the promise of natural cures and holistic wellness. Wellness influencers have hailed this plant-based compound as a cure for many health concerns. 

From immune system support to antioxidant properties, the benefits of quercetin have been touted with fervor. However, beneath the surface of these claims lies a complex and nuanced reality that often goes unmentioned.

What does quercetin do to your body?

Quercetin, a naturally occurring flavonoid, has gained prominence for its potential health benefits and its presence in various fruits, vegetables, and supplements. 

On our journey to understand quercetin, it’s crucial to unravel its sources, mechanisms of action, and the potential positive effects it might offer.

Natural sources of quercetin

Quercetin is abundant in various plant-based foods, ranging from apples, onions, and berries to leafy greens and citrus fruits. The colorful pigments of these foods often indicate their quercetin content. 

Certain herbs like gingko biloba and St. John’s wort also contain notable amounts of this compound.

Mechanisms of action

Quercetin is lauded for its antioxidant properties, which contribute to its potential health benefits. It acts as a scavenger of harmful free radicals, molecules that can damage cells and contribute to chronic diseases. 

Moreover, quercetin is believed to possess anti-inflammatory properties that can play a role in reducing inflammation within the body.

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Potential health benefits of quercetin

1. Immune system support

Quercetin has been linked to potential immune-boosting effects by enhancing the function of immune cells and modulating inflammatory responses [1]. This has led to claims that it could help combat common illnesses.

2. Antioxidant effects

As a powerful antioxidant, quercetin may aid in neutralizing oxidative stress, a factor implicated in various chronic diseases, including heart disease and certain types of cancer.

3. Improves cardiovascular health

Some research suggests that quercetin might contribute to cardiovascular health by improving blood vessel function and reducing blood pressure, which could potentially lower the risk of heart disease.

4. Anti-inflammatory effects

Quercetin’s anti-inflammatory properties have sparked interest in its potential role in managing inflammatory conditions like arthritis.

5. Brain health

Emerging studies propose that quercetin might have neuroprotective effects, possibly contributing to cognitive health and potentially reducing the risk of neurodegenerative disorders.

brain health

What are the negative effects of quercetin?

As the allure of quercetin’s potential benefits takes center stage, it’s imperative to cast a discerning eye on the less illuminated aspects of its consumption. 

While wellness influencers often champion quercetin as a natural remedy, a more comprehensive view reveals that this compound isn’t without its potential drawbacks and unanswered questions.

Lack of long-term studies

The majority of quercetin research has been conducted over relatively short periods, leaving a gap in our understanding of its long-term effects.

This gap becomes more pronounced as quercetin gains popularity as a daily supplement, necessitating more longitudinal studies to assess its impact on health over extended periods.

Limited scientific consensus

Despite the enthusiasm surrounding quercetin, a noteworthy challenge lies in the lack of comprehensive scientific consensus regarding its effects. 

While some studies suggest positive outcomes, others yield inconclusive results or indicate potential concerns. This variability underscores the need for more rigorous research before definitive conclusions can be drawn.

Potential side effects of quercetin

1. Allergic reactions

While quercetin is generally considered safe, some individuals may experience allergic reactions, including skin rashes, itching, and respiratory symptoms. Cross-reactivity with other plant compounds might exacerbate these reactions.

2. Gastrointestinal distress

High doses of quercetin, especially when taken in supplement form, have been linked to gastrointestinal discomfort, including stomach upset, cramps, and diarrhea.

3. Interactions with medications

Quercetin’s ability to influence enzymes involved in drug metabolism raises concerns about potential interactions with various medications. 

This might impact drug efficacy or increase the risk of adverse effects.

4. Kidney health

In some cases, high doses of quercetin have been associated with potential kidney issues, including kidney stones and impaired kidney function.

5. Neurological effects

Contrary to its potential neurological benefits, high concentrations of quercetin have been implicated in certain neurological effects, including seizures. This serves as a reminder that moderation is key.

Can quercetin cause allergic reactions?

It is equally important to address the less-discussed topic of possible allergic reactions that can arise from its consumption. Just as with any natural compound, individuals may exhibit varying responses to quercetin, some of which might manifest as allergic reactions.

Cross-reactivity with other plant compounds

Quercetin’s structural similarity to other flavonoids and plant compounds can lead to cross-reactivity in individuals with existing allergies. This means that if someone is allergic to a certain pollen or food, they might also experience allergic reactions when exposed to quercetin-rich foods or supplements.

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Allergic responses to quercetin

1. Skin reactions

Allergic contact dermatitis is a possible skin reaction triggered by direct contact with quercetin-rich substances. This can result in redness, itching, swelling, and even blisters in more severe cases.

2. Respiratory symptoms

Inhaling airborne particles containing quercetin, such as powders or pollen, might lead to respiratory allergic reactions [2]. Symptoms can include sneezing, congestion, wheezing, and shortness of breath.

3. Oral allergy syndrome

Some individuals who are allergic to certain pollen may experience oral allergy syndrome when consuming foods high in quercetin. This can cause itching, tingling, or swelling in the mouth and throat.

Managing allergic reactions

If you suspect you might be allergic to quercetin or experience any allergic symptoms after consumption, it’s important to take appropriate measures:

  • Discontinue use: If you’re taking quercetin supplements and notice any adverse reactions, cease use immediately and consult a healthcare professional.
  • Consult a doctor: If you have a history of allergies or experience severe symptoms, consult an allergist or physician for proper evaluation and guidance.
  • Read labels: Be vigilant about reading supplement labels and food packaging to check for quercetin content. This can help you avoid accidental exposure.
managing allergic reactions
Photograph: krisprahl/Envato

What does quercetin do to your brain?

Amidst the discussions of quercetin’s potential health benefits, an area that often remains in the shadows is its impact on neurological health. 

Some studies suggest that quercetin may have positive effects on the brain and nervous system, but a more comprehensive exploration reveals that the relationship between quercetin and neurological function is intricate and not entirely understood.

Neuroprotective potential

1. Anti-inflammatory properties

Quercetin’s anti-inflammatory properties may extend to the brain, where inflammation is linked to neurodegenerative disorders like Alzheimer’s and Parkinson’s diseases. 

Some research suggests that quercetin could potentially help mitigate inflammation in the brain.

2. Antioxidant effects

Quercetin’s role as an antioxidant could offer protection against oxidative stress, which is implicated in developing neurodegenerative conditions [3]. This has sparked interest in its potential to slow down cognitive decline.

Potential cognitive benefits

1. Memory and learning

Some animal studies indicate that quercetin might enhance memory and learning abilities by promoting the growth of neurons and supporting synaptic plasticity.

2. Anti-amyloid effects

Amyloid plaques are characteristic features of Alzheimer’s disease. Research in animal models suggests that quercetin might inhibit the formation of these plaques, offering a potential avenue for Alzheimer’s disease prevention.

The complexity of the brain

The brain is a complex organ, and the interactions between compounds like quercetin and its various components are intricate. 

While preliminary research is promising, it’s important to interpret these findings cautiously and acknowledge that the brain’s response to quercetin might vary widely among individuals.

Can quercetin cause digestive issues?

As the popularity of quercetin continues to rise, an often-overlooked aspect of its consumption is its potential impact on gastrointestinal health. 

Quercetin is celebrated for its potential health benefits, particularly its antioxidant and anti-inflammatory properties, but some individuals might experience gastrointestinal discomfort when incorporating it into their diets or supplement regimens.

Potential gastrointestinal reactions

1. Stomach upset

Some individuals, particularly when taking high doses of quercetin supplements, might experience stomach discomfort, including feelings of fullness, bloating, and mild nausea.

2. Cramps and diarrhea

High doses of quercetin, especially when consumed in supplement form, have been associated with gastrointestinal symptoms such as cramps and diarrhea.

Individual sensitivities

The susceptibility to gastrointestinal distress can vary significantly from person to person. 

Factors such as an individual’s overall digestive health, existing sensitivities, and the form in which quercetin is consumed (such as supplements or food sources) can all influence whether such reactions occur.

Mitigating gastrointestinal discomfort

  • Moderation: If you’re considering quercetin supplements, starting with a lower dose and gradually increasing it might help your digestive system acclimate to the compound.
  • Food sources: Incorporating quercetin-rich foods into your diet, such as apples, berries, and onions, might be gentler on the stomach compared to higher-dose supplements [4].
  • Combining with other nutrients: Pairing quercetin-rich foods with foods that contain digestive aids, such as fiber, might help mitigate gastrointestinal discomfort.

Final takeaways

As we draw the curtain on our exploration of quercetin’s potential benefits and lesser-discussed drawbacks, it becomes evident that the story of this compound is multi-faceted. 

Quercetin’s rise to fame in the realm of wellness is underscored by its antioxidant prowess, immune-boosting potential, and possible positive effects on various health concerns.

However, the allure of these benefits often obscures the need for a balanced perspective—one that acknowledges the potential side effects and uncertainties that accompany its consumption.


Is quercetin safe for everyone?

Quercetin is generally considered safe for most individuals when consumed through foods. However, those with allergies, sensitivities, or preexisting health conditions should exercise caution and consult healthcare professionals before incorporating quercetin supplements into their regimen.

Can quercetin interact with medications?

Quercetin has the potential to interact with certain medications by affecting their absorption or metabolism. If you’re on medication, especially blood thinners or medications that impact the liver, consult a healthcare professional before taking quercetin supplements.

Are there natural food sources of quercetin?

Yes, quercetin is naturally found in various foods, including apples, onions, berries, citrus fruits, leafy greens, and certain herbs. Consuming these foods as part of a balanced diet can provide a source of quercetin.

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[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808895/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6273625/
[3] https://www.mdpi.com/2076-3921/12/7/1418
[4] https://www.healthline.com/nutrition/quercetin

The information included in this article is for informational purposes only. The purpose of this webpage is to promote broad consumer understanding and knowledge of various health topics. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this website.