from LONG COVID ESSENTIALS
a resources series by The Sick Times x Long COVID Justice
People with Long COVID often experience new or worse reactions to foods or other things they could previously eat or encounter without issues. These symptoms can be related to cells called “mast cells.” When activated, mast cells release chemicals that cause inflammation, such as histamine.
People experiencing these reactions may have Mast Cell Activation Syndrome (MCAS). MCAS can include sensitivities to foods, fragrances, medications, and other chemicals. Reactions to these can cause a wide variety of debilitating symptoms.
COMMON MCAS SYMPTOMS
- Allergic: Congestion, runny nose, coughing, sneezing, itching, hives, and sometimes anaphylaxis (severe allergic reaction)
- Dermatological: Rashes, flushing, burning sensations
- Gastrointestinal: Diarrhea, constipation, stomach pain after meals
- Neurological: brain fog, fatigue, anxiety, depression
High histamine foods that can cause symptoms:
- Alcohol
- Fermented foods (like yogurt, miso, sauerkraut)
- Sugary drinks
- Tomatoes
- Aged cheeses
- Some nuts
- Citrus
- Chocolate
- Caffeine
- Spinach
- Preserved foods like deli meat
Over time leftovers can develop higher histamine content, causing symptoms. To avoid this, some people cook large batches of food that can be immediately frozen in individual portions, then reheated one at a time to eat later.
MCAS and histamine issues can also make people sensitive to fragrances and chemicals, like cleaning products. Many MCAS patients react poorly to medications (or the other ingredients in them), or can only tolerate small doses of them.
Possible causes of MCAS after COVID-19 include:
- COVID-19 can cause widespread inflammation and mess up the immune system, which includes mast cells. Mast cells regulate the production of inflammation-related chemicals, so when they are overactive, they cause reactions.
- There may be a genetic component making some people more likely to develop MCAS. People with pre-existing allergies may be at higher risk.
- Exposure to toxic mold, chemicals, and airborne allergens may also increase the risk.
People who have MCAS also often have: POTS, interstitial cystitis, gluten and milk intolerance, irritable bowel syndrome.
DIAGNOSIS
MCAS is difficult to officially diagnose. Your doctor may test histamine and tryptase levels in the blood and/or through a 24-hour urine sample. But these tests are imperfect.
Beyond tests, diagnosis is largely based on symptoms and response to treatment. If a low-histamine diet helps you, you may have MCAS.
Symptom ManagemENT
Though there is no cure for MCAS or histamine problems, some medications can help. Be careful to start at low doses to avoid symptom flares and see what works for you. Following a low histamine diet can help manage symptoms. As symptoms improve, try slowly reintroducing certain foods.
Medications that can also help control symptoms include:
- H1 and H2 antihistamines
- Over-the-counter H1 antihistamines such as cetirizine (Zyrtec), fexofenadine (Allegra), loratadine (Claritin)
- Antihistamine nasal sprays
- Prescription H1 antihistamines like hydroxyzine (Atarax or Vistaril)
- H2 antihistamines such as famotidine (Pepcid)
- Asthma inhalers
- Mast cell stabilizers like cromolyn sodium (oral, nebulized or nasal spray form), ketotifen (both antihistamine and mast cell stabilizer)
- Leukotriene inhibitors like Montelukast (Singulair)
- Supplements like Quercetin
- Biologics targeting Mast Cells (Monoclonal Antibodies)
- Omalizumab (Xolair)
- Short or longer-term corticosteroid treatment
- Epi-pen, for anaphylaxis
- DAO supplementation before meals (and other supplements)
- Low-Dose Naltrexone
RESOURCES
- Article about MCAS – Rupa Health
- Approach for patients – PatientPop
- MCAS resource page – RTHM
- Histamine Intolerance facts – Dr. Tina Peers
Writer: Laura Weiss • Betsy Ladyzhets • Medical reviewer: Dr. Alba Azola
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Notes
- This series was published in fall 2024; some information may be subject to change.
- Although each topic has been reviewed by medical professionals, they are informational resources, not medical advice. Always talk to your medical providers before trying treatments or symptom management strategies.
- Each resource page offers brief information and is not comprehensive. We know there is much more information on each topic we cover, and that there are additional topics not yet addressed in this series.