How a Past Viral Infection Can Influence Hay Fever Symptoms
Have you experienced worsening seasonal allergies since recovering from severe acute respiratory syndrome? You’re not alone. Researchers suspect this increase may be due to long haul syndrome (LC) and mast cell activation syndrome (MCAS) — a characteristic found in both LC and seasonal allergies. Could it be the immune system dysregulation associated with severe acute respiratory syndrome is showing up again with an uptick of hay fever symptoms?
Severe Acute Respiratory Syndrome (SARS), Long Haul, and Seasonal Allergies: What’s The Connection?
Many telltale signs of SARS are similar to seasonal allergies: cough, difficulty breathing, running nose, headache, red eyes, irritated skin. Long haul syndrome and hay fever symptoms also overlap: difficulty breathing, fatigue, headache, sneezing. Because of this it can be a challenge to know what you are actually dealing with when the symptoms of each are the same. Adding to the complexity, heightened mast cell activation is also involved in all three conditions, suggesting the connection between long haul syndrome and worsening allergies isn’t just coincidental — it may be rooted in the same immune system dysfunction.
A question I hear often is, what are mast cells? They are a type of white blood cell that play a central role in your immune system, standing guard and releasing histamines along with other powerful biochemicals that fight off illness, infection, or harmless allergens mistakenly viewed as a threat. When mast cells become overly active, it can lead to classic allergy symptoms and allergic flares.
Mast cell activation is also associated with long haul syndrome (LC), based on the findings of a study from 2021.1 The researchers believe that hyper-inflammation caused by the SARS-CoV-2 virus is due to excessive mast cell activation. It was a medium sized study with 136 subjects (89.7% females, age 46.9 ±12.9 years), 136 controls (65.4% females, age 49.2 ±15.5), and 80 MCAS patients (85.0% females, age 47.7 ±16.4).
Importantly, this increased activity also mimicked the symptoms and severity of MCAS. The team concluded that “increased activation of aberrant mast cells induced by SARS-CoV-2 infection by various mechanisms may underlie part of the pathophysiology of LC.”
A later study in 2022 established an association between LC, mast cell activation, and an increase of hay fever symptoms. The authors noted, “It is suggested that immune disturbance from SARS-CoV-2 infection may lead to aberrant mast cell activation and further initiate cascades of inflammatory responses contributing to allergic flare-up.”4
If this describes you, there’s good news. Lifestyle, diet, and herbal remedies can help to calm mast cell activation and reduce the symptoms of seasonal allergies — including sneezing, runny nose, cough, fatigue, and itchy eyes. Let’s take a look at a few below.
Taming Mast Cell Activation During the Allergy Season and Beyond
Follow a Low-Histamine Diet
Since mast cells release histamine, reducing dietary histamine takes a significant burden off an already overloaded system. Foods to limit or avoid include:
- Fermented foods — yogurt, kombucha, sauerkraut, wine, beer
- Aged cheeses
- Processed and cured meats
- Leftover foods — histamine increases as food ages
- Vinegar and vinegar-based foods
- Canned and smoked fish
- Tomatoes, spinach, eggplant, citrus, strawberries, and bananas
Key Nutrients & Supplements
Quercetin. One of the most well-researched natural mast cell stabilizers. Quercetin is a flavonoid found in foods like apples, onions, and capers.
Vitamin C. A powerful natural antihistamine that helps break down excess histamine in the body, vitamin C also supports the adrenal glands, which play a role in regulating the inflammatory response.
Vitamin D. Low vitamin D levels are strongly associated with mast cell dysfunction and immune dysregulation.
Magnesium. Helps to regulate the nervous system and calm the stress response — both of which directly influence mast cell reactivity.
DAO Enzyme (Diamine Oxidase). An enzyme responsible for breaking down histamine in the gut, DAO taken before meals can significantly reduce histamine load from food.
Luteolin. A flavonoid similar to quercetin with strong mast cell stabilizing and anti-inflammatory properties. Found naturally in celery, parsley, and chamomile.
Omega-3 Fatty Acids. Found in fish oil, flaxseed, and chia seed, omega-3s help calm inflammation and reduce mast cell reactivity over time.
Herbs & Botanicals
Stinging Nettle. One of nature’s most effective natural antihistamines. Studies suggest nettle leaf inhibits several key inflammatory pathways involved in allergic response, including mast cell activation.2
Butterbur. Well studied for its ability to reduce histamine-driven symptoms, particularly in the respiratory tract. Look for PA-free butterbur supplements for safety.3
Holy Basil (Tulsi). An adaptogenic herb that helps regulate the stress response and calm immune overactivation — both of which directly impact mast cell stability.
Chamomile. Rich in luteolin and apigenin, chamomile is a gentle but effective mast cell stabilizer. *Note: if you have a known ragweed allergy, chamomile may trigger cross-reactivity and should be avoided.
Resveratrol. Found in grapes and Japanese knotweed, resveratrol has demonstrated mast cell stabilizing properties.
Lifestyle Practices
Stress is a powerful mast cell trigger since the nervous system and the immune system are closely intertwined. Adopt stress-relieving practices, such as:
- Daily prayer and meditation
- Gentle movement like walking and yoga
- Breathwork and methods that tone your vagal nerve
- Adequate sleep — mast cell activity increases significantly with sleep deprivation. See our Sleep Blend if you need an extra layer of support.
Support Your Gut
Since the gut houses such a high concentration of mast cells, gut health and mast cell stability are inseparable. Focus on healing leaky gut, calming intestinal inflammation, and supporting a healthy microbiome. Our Balanced Gut Blend is an outstanding option. Also avoid inflammatory foods that irritate the gut lining — especially refined sugar.
Reduce Environmental Triggers
Mast cells react to more than just food. Common environmental triggers include:
- Mold — one of the most significant and overlooked mast cell triggers
- Fragrances and synthetic chemicals in cleaning and personal care products
- EMF exposure
- Extreme temperature changes
- Heavy metals
Action Steps: Calming Mast Cell Activation — Where to Begin
- Switch to a low-histamine diet for 4 weeks
- Add quercetin, vitamin C, and stinging nettle daily
- Optimize your vitamin D levels
- Address stress as a non-negotiable daily practice — see Nicole’s Apothecary Anxiety & Stress Blend.
Use healing botanicals for an extra support, like those found in our Balanced Gut Blend and Lung Support Bundle
Comprehensive Herbal Support for Allergy Symptoms
Our Lung Support Bundle contains five unique botanical extracts to soothe bronchial passages, ease nasal congestion, and cool respiratory inflammation; calm the histamine response and inhibit mast cell activation. These powerfully effective herbal tinctures for the allergy season include: dual-extracted, fruiting body reishi and cordyceps medicinal mushrooms, stinging nettle, and yerba santa.
This bundle also includes our Bronchial Blend formulation, which contains lungwort lichen and mullein leaf extracts to clear mucus from the bronchial passages, calm coughing and wheezing, ease tightness, and address inflammation in the respiratory tract.
Almost instant allergy symptom-relief. Finally!
“Dries you up fast! Almost instant allergy symptom-relief. I have bad allergies – really bad allergies. The Yerba Santa plus Stinging Nettle is the ONLY thing that has worked for me. I tried everything else but nothing else worked. I use this for symptom-relief to dry up the mucus and it WORKS! Thank you so much – I’m telling my family and friends about it too!” -Maria R.
Shop our Lung Support Bundle today and breathe easier this allergy season.
Frequently Asked Questions
Can severe acute respiratory syndrome trigger worse seasonal allergies?
Yes. Researchers believe the immune dysregulation caused by the virus leaves mast cells chronically overactivated — amplifying the histamine response and intensifying allergy symptoms like sneezing, congestion, fatigue, and itchy eyes long after recovery.
What is mast cell activation syndrome (MCAS)?
MCAS is a condition in which mast cells become chronically overactive in response to triggers that wouldn’t normally cause a reaction. Symptoms range from allergy-like sneezing, itching eyes, and congestion to digestive issues, skin reactions, fatigue, and difficulty breathing.
What foods should I avoid with mast cell activation or histamine intolerance?
Prioritize fresh, whole foods and limit anything that raises histamine levels — fermented foods, aged cheeses, processed meats, leftovers, vinegar, canned fish, and high-histamine produce like tomatoes, spinach, citrus, and strawberries.
What are the best natural supplements for mast cell activation?
Quercetin, vitamin C, vitamin D, magnesium, luteolin, DAO enzyme, and omega-3 fatty acids are the most well-researched options.
What herbs best support mast cell stability and allergy relief?
Stinging nettle and butterbur are the most clinically studied — with butterbur shown in head-to-head trials to perform comparably to the drug Cetirizine without the sedating side effects. Holy basil, chamomile, and resveratrol are helpful as well.
Can stress make allergies and mast cell activation worse?
Yes. The stress response and mast cell activation are deeply linked — when one is active, so is the other.
How does gut health affect mast cell activation?
The gut houses one of the highest concentrations of mast cells in the body. A damaged intestinal lining allows more triggers through, fueling chronic overactivation. Healing leaky gut, reducing intestinal inflammation, and supporting a healthy microbiome are essential for long-term relief. See Nicole’s Apothecary Balanced Gut Blend for an all-in-one gut healing formulation,
What is the best herbal support for allergy and respiratory symptoms?
Nicole’s Apothecary Lung Support Bundle combines five powerful botanical extracts — Reishi, Cordyceps, Stinging Nettle, Yerba Santa, and a Bronchial Blend to calm the histamine response, inhibit mast cell degranulation, clear bronchial passages, and support easier breathing.
Nicole’s Apothecary Products in this Post
Anxiety & Stress Tincture
Balanced Gut Blend Tincture
Allergy & Asthma Support Bundle
Sleep Blend Tincture
Stinging Nettle Tincture
Yerba Santa Tincture
References
- Mast cell activation symptoms are prevalent in Long-COVID
Weinstock, Leonard B. et al. International Journal of Infectious Diseases, Volume 112, 217 – 226 - Bakhshaee, Mehdi et al. “Efficacy of Supportive Therapy of Allergic Rhinitis by Stinging Nettle (Urtica dioica) root extract: a Randomized, Double-Blind, Placebo- Controlled, Clinical Trial.” Iranian journal of pharmaceutical research : IJPR vol. 16,Suppl (2017): 112-118.
- Blosa, M., Uricher, J., Nebel, S., Zahner, C., Butterweck, V., & Drewe, J. (2021). Treatment of Early Allergic and Late Inflammatory Symptoms of Allergic Rhinitis with Petasites Hybridus Leaf Extract (Ze 339): Results of a Noninterventional Observational Study in Switzerland. Pharmaceuticals, 14(3), 180. https://doi.org/10.3390/ph14030180
- Koc, Ho Cheng et al. “Long COVID and its Management.” International journal of biological sciences vol. 18,12 4768-4780. 11 Jul. 2022, doi:10.7150/ijbs.75056
