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Quercetin - What It Is and What It Can Do

Updated: Feb 17

Quercetin is a plant flavonoid found in many berries, grapes, cherries, kale, lettuce, cabbage, asparagus, peppers, cruciferous vegetables, and other plant foods. Quercetin is abundant in antioxidants and offers many health benefits, including reduced risk of neurodegeneration, diabetes, cancer, and other chronic health issues. Quercetin is also a natural antihistamine that helps to reduce symptoms of allergies, histamine intolerance, and mast cell activation syndrome while regulating your immune system.

In today’s article, I want to discuss the benefits of quercetin. I will outline the benefits of quercetin for histamine intolerance and other health issues. I will offer a list of foods that are high in quercetin and tips for supplementation.

What Is Quercetin

Quercetin is a pigment and plant flavonoid. Flavonols are plant compounds found in vegetables, fruits, tea, grains, and wine. Flavonoids, including quercetin, have been known for reducing the risk of heart disease, neurodegenerative disorders, cancer, and other chronic conditions (1, 2).

One of the major benefits of quercetin is its antioxidant effects and ability to neutralize free radicals (3). Reducing free radical damage and oxidative stress may help to reduce the risk of diabetes, heart disease, cancer, and other chronic diseases (4). Quercetin is one of the most abundant flavonoids found in your diet with powerful antioxidant, anti-inflammatory, immune-supporting, allergy-fighting, antithrombotic, and other health benefits (5).

Foods High in Quercetin

Quercetin is found in abundance in many plant foods.

Fruits high in quercetin include:

  • Blueberries

  • Chokeberries

  • Cranberries

  • Bilberries

  • Blackberries

  • Black currants

  • Grapes

  • Apples

  • Black plums

  • Cherries

Greens and vegetables high in quercetin include:

  • Romaine lettuce

  • Red leaf lettuce

  • Kale

  • Cabbage

  • Chicory greens

  • Peppers

  • Red onion

  • Broccoli

  • Cruciferous vegetables

  • Asparagus

  • Snap peas

  • Shallot

  • Capers

  • Scallion

Other plant-based foods high in quercetin include:

  • Sage

  • Thyme

  • Dill

  • Tarragon

  • Chives

  • American elder

  • Gingko Biloba

  • St. John’s wort

  • Buckwheat

  • Green tea

  • Black tea

  • Elderberry tea

  • Olives

  • Olive oil

  • Red wine

Quercetin and Histamine

Quercetin is a natural antihistamine that can reduce the allergic response in your body while supporting your immune system and overall health. By inhibiting the release of histamine, reducing proinflammatory cytokine production, and supporting a Th1 and Th2 immune response balance, quercetin may reduce sneezing, runny nose, sinus congestion, watery eyes, itchy skin, rashes, other allergy symptoms, and other symptoms of histamine intolerance. It’s no surprise that quercetin is an ingredient of some anti-allergy medications that reduce pro-inflammatory cytokines and function as immunomodulators (6).

According to a 2007 study published in Inflammation Research, quercetin may reduce inflammation in the airways and respiratory symptoms caused by allergies (7). A 2012 study published in PLoS One has found quercetin can block mast cell inflammatory cytokine release (8). Researchers found that this benefit of quercetin is so powerful that it may make quercetin more effective for contact dermatitis and photosensitivity than Cromolyn, a drug commonly used for mastocytosis and mast cell disorders.

A 2016 review published in Molecules has found anti-allergic benefits of quercetin lie in its ability to inhibit histamine release, reduce proinflammatory cytokines, suppress leukotriene creation and interleukin IL-4 production, support the immune system, and offer antioxidant benefits (9). A 2020 review published in Allergy, Asthma & Clinical Immunology has explained that quercetin can suppress histamine production, reduce the release of pro-inflammatory mediators, support Th1/Th2 balance, and reduce antigen-specific IgE antibody release (10).

Researchers found that due to its anti-histamine, immunomodulatory, and anti-inflammatory properties, quercetin may be effective for allergic rhinitis (AR), allergic asthma, and atopic dermatitis (AD). They noted that since quercetin is natural, affordable, and has few to no side effects, dietary quercetin and supplementation may be a great natural therapeutic option for allergic diseases. The benefits of quercetin may be supportive for those with seasonal allergies, allergic diseases, histamine intolerance, and mast cell activation syndrome (MCAS) (10).

Other Health Benefits of Quercetin

The benefits of quercetin go way beyond reducing histamine levels. Other benefits of quercetin may include the following:

Reduced Inflammation

Chronic inflammation is one of the root causes of most chronic symptoms and diseases. One of the benefits of quercetin is reducing inflammation, thus potentially lowering the risk of chronic conditions and the symptoms of inflammatory problems. According to a 2017 study, quercetin may help to reduce inflammation and disease severity in rheumatoid arthritis (11).

Better Brain Health

Another benefit of quercetin is improved brain health and reduced risk of brain degeneration. A 2015 animal study published in Neuropharmacology has found that quercetin may help to reduce symptoms of Alzheimer’s disease and improve cognition and learning (12). A 2016 review published in Oxidative Medicine and Cellular Longevity has found that quercetin may help to reduce the risk of dementia, Alzheimer’s disease, and other degenerative brain disorders due to its antioxidant benefits (13).

Improved Blood Pressure

High blood pressure is a rampant health issue in North America. It can raise the risk of heart disease. According to a 2002 animal study published in the Journal of Experimental Pharmacology and Experimental Therapeutics, quercetin may have vasodilator effects and may help to lower blood pressure (14). A 2001 animal study published in the British Journal of Pharmacology has also found that quercetin may help to lower blood pressure (15).

Reduced Risk of Cancer

Because of the antioxidant benefits of quercetin, it may also help to reduce the risk of cancer. According to a 2009 review published in Recent Patents of Inflammation & Allergy Drug Discovery, quercetin may help to reduce inflammation, oxidative stress, and the risk of cancer (16). Several recent research studies have found that quercetin may help to reduce the growth of cancer and trigger cell death in prostate, lung, breast, ovarian, bladder, liver, colon, lymphoid, blood, and adrenal cancer cells (17, 18, 19, 20).

Improved Blood Sugar

Improving blood sugar levels is another benefit of quercetin. According to a 2019 review published in Phytochemical Research, quercetin may help to balance blood sugar levels and reduce the risk of metabolic disease (21). Another 2019 review published in Biomedicine & Pharmacotherapy has found that quercetin may help to reduce the risk of diabetes (22). Another 2019 review published in Food and Chemical Toxicology has also found that quercetin may help to reduce blood sugar (23).

Better Exercise Performance

Quercetin may also aid your exercise performance. A 2011 review published in Medicine and Science in Sports Medicine and Exercise has found that quercetin may help to improve endurance and exercise capacity (24). According to a 2014 study published in the International Journal of Preventative Medicine, quercetin may help to improve exercise performance, reduce muscle damage, and improve body composition (25).

Anti-Aging Effects

Another benefit of quercetin is anti-aging. According to a 2017 study published in the International Journal of Preventative Medicine, quercetin may help to improve aging markers on kidney cells (26). A 2018 study published in The American Journal of Chinese Medicine has found that quercetin may help to reduce aging in the human dermal fibroblast (HDF) of your skin (27). A 2018 study published in Nature Medicine has found that senolytics and quercetin combined may help to improve physical function and increase lifespan in older people (28).

How to Use Quercetin

If you are experiencing symptoms of allergies, histamine intolerance, or MCAS and want to experience the benefits of quercetin, I recommend consuming plenty of quercetin-rich fruits, greens, vegetables, herbs, and other plant foods. Additionally, I recommend taking a high-quality quercetin supplement for its antihistamine, antioxidant, anti-inflammatory, immune-boosting, and other health benefits. A common dose is 500 mg three times daily, taken with meals. When combined with other nutraceuticals, the dose may be lower.

You will notice that many quercetin supplements also include bromelain. Bromelain is an enzyme that helps to improve the bioavailability and positive effects of quercetin. Quercetin with bromelain may help to fight allergic reactions and increased histamine response more effectively. Some supplements combine quercetin with resveratrol, curcumin, or other anti-inflammatory herbs to reduce inflammation and support your immune system.

In addition to using quercetin for reducing histamine levels, I recommend following a low-histamine diet and reducing your histamine bucket by reducing stress, moving your body, sleeping plenty, and lowering environmental toxin exposure.

Next Steps

Are you experiencing symptoms of histamine intolerance or MCAS? Are you interested in what treatment options are best for your situation? Working with a healthcare practitioner knowledgeable about histamine intolerance and MCAS is the best way to get to the root cause of your symptoms and to create an individualized treatment plan. I welcome you to start a functional medicine consultation with me for further personalized guidance to improve your health. You may book your consultation here. Check out my Histamine Intolerance Course here. Learn on your own time, from anywhere. Get an inside look at the most helpful functional medicine tests for pinpointing imbalances, ways to identify and manage the most common (and sometimes surprising) mast cell triggers, and learn what to eat, what to avoid, and why.


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