Understanding the Link Between Endometriosis and MCAS

For many people living with endometriosis, the pain, inflammation, and fatigue don’t tell the whole story. A growing number of patients are discovering that their symptoms overlap with another condition: Mast Cell Activation Syndrome (MCAS). While research is still emerging, the relationship between Endo and MCAS is becoming too significant to ignore.

What Is MCAS?

Mast Cell Activation Syndrome happens when mast cells, immune cells involved in allergic and inflammatory responses, become overly sensitive or frequently activated. Instead of releasing chemicals (like histamine) only during infections or allergic reactions, they release them too often or in excessive amounts.

Common MCAS symptoms include:

• Hives, flushing, itching

• Gastrointestinal issues (nausea, diarrhea, bloating)

• Extreme fatigue

• Brain fog

• Headaches or migraines

• Respiratory symptoms

• Sensitivity to foods, temperature, scents, or medications

These symptoms often overlap with what Endo patients already experience, which can make diagnosis confusing.

Why Endometriosis & MCAS Often Show Up Together

Shared Inflammation Pathways

Endometriosis is a chronic inflammatory disease. MCAS is a disorder involving abnormal inflammatory triggers.

Both conditions involve:

• High histamine levels

• Immune system dysregulation

• Heightened inflammatory responses

This means that an already inflamed body (Endo) may be more vulnerable to mast cell overactivation (MCAS).

Mast Cells Are Found Inside Endo Lesions

Studies show mast cells are abundant in endometriosis lesions, especially deep infiltrating lesions. These mast cells release histamine and other inflammatory chemicals that:

• Worsen pain

• Increase nerve irritation

• Amplify pelvic inflammation

  
  

This may explain why some patients experience severe allergic-type symptoms during flare-ups.

Hormones Influence Both Conditions

Endometriosis responds to hormonal changes — especially estrogen. MCAS symptoms also worsen when estrogen is high.

This is why many patients report:

• Flares around ovulation

• Worsening symptoms during high-estrogen phases of the cycle

• Difficulty tolerating certain hormonal medications

  
  

Hormones, mast cells, and inflammation are tightly linked.

Gastrointestinal Overlap

Endometriosis commonly affects the bowel, causing:

• Bloating

• Nausea

• Food sensitivities

• IBS-like symptoms

  
  

MCAS also affects the GI tract. For some patients, the underlying issue isn’t “IBS” — it’s mast-cell-driven inflammation that worsens during Endo flares.

Shared Triggers

Patients with Endo and MCAS often flare due to the same triggers:

• Stress

• Heat sensitivity

• Certain foods (gluten, dairy, alcohol, fermented foods, high-histamine foods)

• Infections

• Allergies

• Strong scents or chemicals

• Hormonal fluctuations

  
  

This makes management more complicated, but also helps explain patterns many patients recognize.

How Do You Know If You Might Have Both?

You might consider asking your doctor about MCAS if you live with Endo and experience:

• Unexplained allergic reactions

• Flushing or skin itching without a rash

• Frequent migraines

• Multiple food intolerances

• Sensitivity to medications

• Sudden blood pressure drops, dizziness, or fainting

• Chronic GI symptoms that don’t match imaging or labs

• Flares that seem tied to histamine-rich foods

  
  

MCAS specialists often include allergists, immunologists, and sometimes GI doctors.

Treatment Approaches Patients Find Helpful

While everyone is different, patients commonly find relief from:

Antihistamines

• H1 blockers (cetirizine, loratadine)

• H2 blockers (famotidine, ranitidine before discontinuation)

These reduce histamine-driven symptoms.

Mast Cell Stabilizers

Medications or supplements such as:

• Cromolyn sodium

• Ketotifen

• Quercetin

• Luteolin

  
  

Help reduce mast-cell activation.

Anti-Histamine Diet

Low-Histamine Foods

Avoiding or reducing histamine-rich foods can lower symptom severity.

These foods are generally well-tolerated because they contain minimal histamine and don’t trigger mast-cell release for most people. (Individual reactions can vary.)

✓ Fresh Proteins

• Fresh chicken

• Fresh turkey

• Freshly cooked beef (not aged)

• Fresh fish eaten immediately after cooking

• Fresh lamb

• Eggs

• Fresh tofu (plain, minimally processed)

  
  

✓ Vegetables

(Almost all fresh vegetables except tomatoes, spinach, and eggplant)

• Carrots

• Broccoli

• Zucchini

• Cucumber

• Lettuce, romaine, leafy greens

• Sweet potato

• Potato

• Cauliflower

• Green beans

• Bell peppers

• Celery

• Asparagus

  
  

✓ Fruits

(Non-citrus, non-fermented; avoid dried or overly ripe)

• Apples

• Blueberries

• Pears

• Watermelon

• Mango

• Grapes

• Bananas (just ripe, not overripe)

• Melons

• Papaya

  
  

✓ Grains & Starches

• White rice

• Brown rice

• Quinoa

• Oats

• Millet

• Buckwheat

• Rice noodles

• Rice crackers

  
  

✓ Fats & Oils

• Olive oil

• Coconut oil

• Avocado oil

• Ghee (if tolerated)

  
  

✓ Herbs & Seasonings

• Fresh basil

• Fresh parsley

• Fresh cilantro

• Sea salt

• Ginger

• Turmeric

  
  

✓ Drinks

• Water

• Coconut water

• Herbal teas (chamomile, ginger, rooibos)

  
  
  
  

  High-Histamine Foods

  
  

These foods contain high histamine OR trigger the body to release more histamine, making symptoms worse for many MCAS/Endo patients.

✗ Proteins to Avoid

• Processed meats (ham, bacon, sausage, deli meats)

• Aged meats (steakhouse cuts, dry-aged beef)

• Leftover meat older than 24 hours

• Canned fish (tuna, sardines, anchovies)

• Smoked fish (salmon, mackerel)

• Shellfish

  
  

✗ Dairy

• Aged cheese (cheddar, parmesan, gouda, Swiss)

• Sour cream

• Yogurt

• Kefir

• Buttermilk

  
  

✗ Fruits (histamine-releasing or reactive)

• Strawberries

• Citrus fruits (orange, lemon, lime)

• Pineapple

• Kiwi

• Raspberries

• Dried fruits (raisins, dates, apricots)

  
  

✗ Vegetables

• Tomatoes

• Spinach

• Eggplant

• Sauerkraut (fermented)

• Pickles (fermented/aged)

  
  

✗ Fermented or Aged Foods

• Vinegar & anything with vinegar

• Soy sauce, tamari

• Kimchi

• Kombucha

• Miso

• Tempeh

• Alcohol (wine, beer, champagne)

  
  

✗ Drinks

• Coffee

• Energy drinks

• Alcohol

• Black tea, green tea (can trigger mast cells)

✗ Miscellaneous

• Chocolate

• Nuts (especially cashews, walnuts, peanuts)

• Artificial food dyes

• Leftovers older than a day

• Protein powders (especially whey)

• Canned foods

Anti-inflammatory + Anti-Endo Approach

Many patients manage both conditions with:

• Gentle anti-inflammatory meals

• Stress reduction

• Light movement

• Heat regulation

• Avoiding triggers when possible

Treating Endometriosis Directly

Proper excision surgery and specialist-level care can significantly reduce:

• Pelvic inflammation

• Hormonal triggers

• Mast-cell overstimulation

  
  

Some patients report MCAS improving after proper excision.

The link between Endometriosis and MCAS is becoming clearer each year. Both conditions stem from deep immune system dysfunction, chronic inflammation, and hormonal sensitivity. When they occur together, which is more common than many realize, symptoms can become more severe and widespread.

Understanding this relationship gives patients:

• Better language for self-advocacy

• More accurate treatment strategies

• Validation that their symptoms are real and interconnected

  
  

If you think you might have MCAS on top of Endo, looking into the connection might help you make sense of those symptoms that never quite added up.

#endometriosis #MCAS #histamineintolerance #lowhistaminediet #chronicinflammation

#endo #pelvicpain #womenshealth #chronicillness #endocommunity #endometriosiswarrior