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  • Writer's pictureDr. Brian Lum

Long Covid Symptom: Histamine Intolerance

Updated: 3 days ago

Soon after the onset of the Covid-19 pandemic, Long Covid patients began to appear. These patients experience persistent symptoms long after an initial infection has passed.

These symptoms can range from mild to debilitating and last for weeks, months, or years. Like other instances of post-viral symptoms, patients often find their doctors dismissive and their treatment options severely limited.

Fortunately, functional medicine provides scientifically-backed, natural solutions that are particularly well-suited to complex, chronic symptoms like those found in Long Covid.

a marble statue with a surgical mask. Long Covid and Histamine Symptoms. Logo Dr. Brian Lum

Personal Experience with Long Covid

Many of my family members contracted Covid in March of 2020 and while some recovered quickly, others developed Long Covid.

My experience in nursing them and my wife's skill in symptom mitigation led us to develop effective techniques for reducing the severity of symptoms and supporting the healing process.

In the developed world, we are unused to virulent strains of viruses that blow through the population quickly, claiming large numbers of victims. The flu can cause a fairly high number of deaths each season, but we are largely desensitized to those losses.

The specters of smallpox, yellow fever, and tuberculosis that our ancestors contended with seem far removed from us - and yet it is a mistake to think that we cannot learn from the past and that non-Western forms of medicine are of no use.

Covid-19 is new, but post-viral symptoms are not.

By using nutritional interventions, Chinese medicine principles, functional medicine testing and treatment, Spring Forest Qigong, and personal experience with complex illness, my family achieved a complete recovery.

With a multi-faceted approach, a full resolution of Long Covid symptoms is absolutely possible and is a frequent occurrence in my practice.

Histamine Symptoms after a Covid Infection

One of the many symptoms that can arise from COVID-19 is a newly acquired sensitivity to histamine.

Most patients arrive at this conclusion by looking up their symptoms and seeing that they correlate with 'Histamine Intolerance' or 'Mast Cell Activation Syndrome' or simply by noticing that their symptoms get worse with histamine-releasing or high-histamine foods.

Histamine-Related Symptoms in Long Covid

  • anxiety/panic attacks

  • depression/fearful thoughts

  • insomnia

  • rashes/hives

  • itchy skin

  • reactions to high histamine foods

  • heart palpitations

  • increased allergies

  • nerve pain

  • sinus congestion

  • digestive symptoms

  • dizziness

  • exercise intolerance

  • POTS/dysautonomia

  • brain fog/memory problems

  • fatigue

  • food intolerances/sensitivities

The information in this article and on this website are intended for informational purposes only and does not take the place of seeing a doctor and should not be used for the purposes of diagnosis.  If you are experiencing severe symptoms, have chest pain, or have trouble breathing, go to a hospital right away. Consult a doctor before beginning or stopping any medications or interventions. 

Histamine Sensitivity can manifest as a wide variety of symptoms. These can include an extreme sensitivity to histamine-containing or histamine-inducing foods. For instance, a small bite of salmon can cause severe insomnia and anxiety for multiple days. Dairy cross-contamination can cause painful hives, skin rashes and mood swings.

Heart palpitations (or a feeling that your heart is pounding) are common with Long Covid, as are sinus congestion, skin itchiness, and digestive upset.

High levels of histamine can cause severe anxiety and depression, and many patients report an extremely high level of fear at night. This fear is reported as feeling 'different' even in those patients who are familiar with anxiety symptoms. Histamine-related symptoms tend to peak at night.

Most methods of managing these conditions, even when done with a medical professional, rely heavily on symptom mitigation through histamine avoidance and general advice amounting to pacing yourself.

As with any persistent or severe symptom, it is important to get checked by your primary care physician to rule out any other health condition.

It is also important to know all the things histamine does so that you can move beyond symptom mitigation and into long-term recovery - histamine is, after all, not the problem - the problem is that too much histamine is being released because of a perceived threat sensed by your body.

What is Histamine?

Histamine Overload, rather than Histamine Intolerance or Sensitivity, would be a more accurate characterization of what is going on in Histamine Sensitive patients.

Histamine is an amino acid derivative secreted by basophils (a type of white blood cell), mast cells, and some neurons. [1] It functions as a paracrine secretion (a chemical messenger that affects a small area, also called a local hormone) and neurotransmitter and has a wide range of effects, including gastric secretion, bronchoconstriction, and vasodilation. [2] Histamine can be pro-inflammatory or anti-inflammatory. [3]

Potential Mechanisms of Long Covid Symptoms

The ACE 2 receptor that Covid uses for viral replication to infect the body is also present on mast cells, which can potentially be one of the causes of increased histamine response in Covid and Long Covid patients. (4)

Just as COVID-19 can induce a dangerously strong cytokine response, histamine can act as an inflammatory messenger, triggering additional immune and inflammatory responses.

One thing that may be going on is that an underlying infection (like a root canal that has failed and become infected) has had your histamine 'baseline' levels already high before a COVID-19 infection.

After the infection and resulting debris or tissue damage, the body is unable to handle the double burden of clearing the infectious debris from two infections (one of which is still ongoing).

The underlying infection alone would be classed as "unresolved systemic inflammation," which is recognized as a cause of Long Covid. [5}

An observation from our patient population is that many Long Covid sufferers have an underlying factor of mold exposure. The exposure could be in the distant past or in their present home. When we test their urine mycotoxin levels, they are almost always elevated.

I believe this correlation of mold toxicity and Long Covid may be from the increased mast cell activity from mold/fungal issues, plus the dysregulation of the immune system that mold causes. Testing urine mycotoxins is well worth the effort.

Another theory is that the presence of persistent SARS-CoV-2 in organ and tissue sanctuaries leads to a persistent inflammatory response, causing high histamine. [6]

Essentially, the virus hides out in areas of the body so that instead of your immune system clearing the infection quickly, it takes much longer as your body slowly roots out the virus.

Gastrointestinal/Digestive Symptoms

Food allergies and sensitivities are extremely common in Long Covid patients. This is particularly true with gluten and dairy. Keep in mind that these food sensitivity symptoms can overlap with other, more obvious signs of infection (like cough and fatigue).

Since you feel sick already, it is hard to differentiate between a new food sensitivity and the other symptoms of general illness.

Keep a food journal, and make a note of what symptoms get worse after eating. Rapid heart rate after eating is a common sign of food intolerance, as are migraines, insomnia, and anxiety. Remember that even a very small amount of an offending food (including crumbs) can perpetuate low-grade inflammation in your body, which can cause long-term severe symptoms.

The stomach is affected by Long Covid, as is the vagus nerve (which splits and goes down the esophagus) - these two factors can make eating and digesting difficult. It can feel like food 'sits' in the stomach, fat is not digested well, and rich foods can cause nausea.

In these cases, alcohol-free herbal digestive bitters can be very effective, as can warm water with lemon juice before meals. This can help increase stomach acid and bile production.

As a general rule, processed foods, excess sugar, and cold beverages will be more difficult to digest. Emphasize warm foods, cooked fruits and vegetables, and soups like congee (Chinese rice porridge).

In Long Covid, the pancreas, spleen, and liver are affected and respond well to mast cell stabilizing agents. Specific supplementation will depend on the patient, their age and constitution, and any other symptoms they have. Quercetin has been helpful for many patients.

It is sometimes the case that Long Covid is merely the trigger that tips a long-standing problem into a more obvious problem.

A parasitic infection will become more apparent, small intestinal bacterial overgrowth (SIBO) will become more pronounced, and symptomatic anxiety and depression that were tendencies suddenly become hard to manage.

This is why addressing Long Covid with Functional Medicine is ideal; we can address many underlying imbalances at once.

Nervous System Inflammation

This is a broad category but one that encompasses symptoms that can be otherwise deemed as unimportant.  The development of POTS (Postural orthostatic tachycardia syndrome - when your heart rate increases too quickly when you get up), histamine intolerance, food sensitivities, and heart palpitations are common symptoms in Long Covid.

Any heart-related symptom should be investigated by your primary doctor. Often, however, after any major issues have been dismissed, the patient is left with the symptom and no treatment options. Fortunately, functional medicine is often effective in these instances.

An inflamed nervous system after an acute infection can result in the feeling that your nerves are on a knife's edge and that there is an ever-present baseline of anxiety which is often punctuated by frequent panic attacks.

There is a remarkable similarity among Long Covid patients in the way they describe the anxiety they experience.

They say it is unlike anything they have experienced and unlike 'other' kinds of anxiety - even if they have experienced extreme anxiety in the past. It is often accompanied by the feeling that their nerves are very exposed - they are often called 'oversensitive' by unbelieving or unsupportive family members.

Anything from a small argument to a hot shower to a short walk can trigger a histamine response that can contribute to recurring panic attacks or a sleepless night.

It is important that you are careful with yourself in your recovery and be mindful that it is common for Long Covid patients to have post-traumatic stress disorder (PTSD), either from the initial viral infection or from the resultant illness.

When you have a 'good day,' it can be very tempting to do as much as possible, but pacing is important; you will need to relearn your limits temporarily, as rest in this phase is crucial.

I have found that the books by Dr. Claire Weekes can be very helpful. She was an Australian doctor who specialized in the treatment of post-traumatic stress disorder among soldiers after the First World War at a time when 'nervous illness' was largely ignored or dismissed by doctors at the time.

Mindfulness techniques like Spring Forest Qigong, gentle yoga, and breathing techniques can also help in soothing an inflamed nervous system.

Additional techniques and supplements can also be used and would be specific to an individual; these interventions would be determined at the time of an appointment.

Keep in mind that underlying imbalances - like nutrient deficiencies - can make these symptoms much worse. It is important to get checked for things like Vitamin D and B12 deficiencies which can, when corrected, result in immediate symptom alleviation.

Heart & Metabolic Symptoms

There are some studies that support the idea that targeting histamine receptors can effectively eliminate heart-related Long Covid symptoms; these studies also confirm the role that mast cell activation has in these symptoms. [7]

Some patients have a persistent feeling that they are not getting enough oxygen despite having medical devices confirm that their levels are adequate. This feeling is often accompanied by symptoms of histamine intolerance.

In these cases, it is important (after you have been checked by your doctor) to check if you have optimal iron levels, which ensure that hemoglobin is transferring oxygen well.

If a lower state of oxygen is detected by the body, it will produce more histamine. This may be because it is trying to use histamine and the resultant vasodilation to facilitate oxygen transfer.

Some patients have found relief using hyperbaric oxygen chambers and supplemental oxygen canisters - but as with any intervention, these solutions are not suitable for everyone.

Foods rich in chlorophyll and a diet rich in leafy greens are useful to ease metabolic-related Long Covid symptoms.

Keep in mind that heart and metabolic-related symptoms can also be a result of a newly acquired food sensitivity (common after a COVID-19 infection) as well as blood sugar imbalances.

Eating three meals a day, each with protein, fats, and carbohydrates, is a good first step in ensuring healthy blood sugar levels so that healing can occur.

There is a wide variety of medicines that can ease and resolve neuro-vascular inflammation. One supplement that has been helpful for many patients is SPM - specialized pro-resolving mediators - which is the anti-inflammatory derivative of fish oil.

This supplement can be helpful for patients who are so histamine-sensitive they cannot take anything containing fish oil.

Treating Histamine Sensitivity in Long Covid

Most Long Covid patients experiencing Histamine-related symptoms benefit from following a low-histamine diet. This generally reduces symptoms and overall inflammation, but more can be done to support the body in healing.

Long Covid is still poorly understood; scientists and patients alike have only had a few years to experience and analyze the implications of this virus. This is why practitioners should be open-minded when it comes to unusual or uncharacteristic symptoms and be flexible in devising treatment plans for patients who become sensitive to histamine.

I only mention a few general treatments in this article; this is deliberate and is because there is no one 'protocol' or supplement that fits everyone's symptom presentation. Personalization is key to recovery and something I prioritize in every patient appointment.

Treatment options often depend on symptom severity, an individual's constitution, age, other symptoms, underlying conditions, and even the time of year.

Far too often, patients are being told that there is 'no cure' for Long Covid when recovery is absolutely possible.

Online Consultations Available

For over a decade, I have treated complex and chronic illnesses and patients who are sensitive to conventional treatments. This experience has informed the way I help all my patients but especially those who are experiencing Long Covid.

With functional medicine diagnostics and treatment options, scientifically supported mind/body practices, powerful natural supplements and specific and personalized application - histamine symptoms in Long Covid can be a thing of the past.

I am currently accepting new patients and offer online consultations worldwide.

If you would like to schedule a free 15 minute consultation with me to ask questions about becoming a patient click the link below.


Written by Stephanie Lum and Dr. Brian Lum

Disclaimer: If you think that you may have a medical emergency, call your doctor or 911 immediately. No action or inaction should be taken based solely on the contents of this information. Nor should you ever delay seeking medical advice or treatment due to the information contained on this Website. The information on this Website is not intended to diagnose, treat, cure, or prevent any disease or medical condition. The information discussed is not intended to replace the advice of your healthcare provider. Reliance on the information provided by this Website, Dr. Brian Lum, or Functional Healthcare Institute is solely at your own risk.


[1] Saladin, K. S., Gan, C. A., & Cushman, H. N. (2011). Anatomy & physiology : the unity of form and function (Sixth edition.). McGraw-Hill Education. G-9.

[2] Saladin, K. S., Gan, C. A., & Cushman, H. N. (2011). Anatomy & physiology : the unity of form and function (Sixth edition.). McGraw-Hill Education. G-9.

[3] Thangam EB, Jemima EA, Singh H, Baig MS, Khan M, Mathias CB, Church MK and Saluja R (2018) The Role of Histamine and Histamine Receptors in Mast Cell-Mediated Allergy and Inflammation: The Hunt for New Therapeutic Targets. Front. Immunol. 9:1873. doi: 10.3389/fimmu.2018.01873

[4] Dileepan KN, Raveendran VV, Sharma R, Abraham H, Barua R, Singh V, Sharma R, Sharma M. Mast cell-mediated immune regulation in health and disease. Front Med (Lausanne). 2023 Aug 17;10:1213320. doi: 10.3389/fmed.2023.1213320. PMID: 37663654; PMCID: PMC10470157.

[5] Tang SW, Leonard BE, Helmeste DM. Long COVID, neuropsychiatric disorders, psychotropics, present and future. Acta Neuropsychiatr. 2022 Jun;34(3):109-126. doi: 10.1017/neu.2022.6. Epub 2022 Mar 3. PMID: 35144718.

[6] Galán M, Vigón L, Fuertes D, Murciano-Antón MA, Casado-Fernández G, Domínguez-Mateos S, Mateos E, Ramos-Martín F, Planelles V, Torres M, Rodríguez-Mora S, López-Huertas MR, Coiras M. Persistent Overactive Cytotoxic Immune Response in a Spanish Cohort of Individuals With Long-COVID: Identification of Diagnostic Biomarkers. Front Immunol. 2022 Mar 25;13:848886. doi: 10.3389/fimmu.2022.848886. PMID: 35401523; PMCID: PMC8990790.

[7] Salvucci, Fabrizio, Roberto Codella, Adriana Coppola, Irene Zacchei, Gabriella Grassi, Maria Luisa Anti, Nicolita Nitisoara, Livio Luzi, and Carmine Gazzaruso. 2023. “Antihistamines Improve Cardiovascular Manifestations and Other Symptoms of Long-COVID Attributed to Mast Cell Activation.” Frontiers in Cardiovascular Medicine 10: 1202696–1202696.


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