# MCAS Overview The diagnosis of Mast Cell Activation Syndrome (MCAS) is controversial, with many diagnostic criteria requiring an elevated tryptase level and anaphylactic-level reactions. However, I tend to agree more with Dr. Afrin that MCAS is best diagnosed clinically. Because MCAS is so common in ME/CFS, I often treat it empirically and only rule it out if treatment shows no benefit. MCAS appears to be an underlying cause of orthostatic intolerance, GI distress, various types of pain, systemic inflammation, gut inflammation with malabsorption of micronutrients, and mental illness in many patients with ME/CFS. The mechanism for mast cell hyperactivity appears to be varied, ranging from the mechanical (e.g. hypermobility) to the autoimmune (e.g. celiac disease). It may be caused by leaky gut leading to sensitization of the immune system to food antigens. Mast cells may also lose the stabilizing effect of the vagus nerve as ventral vagal tone is lost. Histamine intolerance symptoms tend to be triggered by foods, heat or allergens (eg. mold or pollen). Reactions may be inconsistent and tend to be more severe after time away from the trigger (which allows the mast cells to build up their stores of histamine and other contents). Symptoms may affect the skin (hives, itching, flushing), GI tract (nausea, vomiting, diarrhea, cramping), cardiovascular system (tachycardia, palpitations, dizziness, presyncope), or the respiratory system and conjunctiva (wheezing, nasal stuffiness, itchy eyes). It also tends to result in fatigue, pain, feeling “inflamed” and anxiety. ## Testing Tryptase, baseline (normal is less than 10) Then rule out mastocytosis and hereditary tryptasenemia ## Protocol Histamine intolerance is treated with a three pronged approach: 1. Antihistamines, H1 and H2 2. Low histamine diet 3. Mast cell stabilization, both pharmaceutical and via increasing vagal nerve tone The final protocol will look like: 1. H1 blocker like Allegra/Zyrtec/Xyzal/Claritin at max dose 2. H2 blocker famotidine, 20 mg twice per day 3. Zafirlukast (leukotriene inhibitor) 20 mg twice daily 4. D-Hist, 2 capsules, three times a day for 7 days (the loading dose), followed by 1 capsule daily or more if needed for symptom control 5. Vitamin C, 1000mg daily 6. Cromolyn 7. Ketotifen 8. Quercatin Additionally, the patient will also be following a Low Histamine Diet and practicing Yoga Nidra or other deep relaxation technique 1-3 times daily. The relaxation technique helps to stabilize mast cells and reduce histamine release. These practices can be started right away at the beginning of the protocol. ## Antihistamines Some people find different antihistamines more efficacious than others. If possible, it's best to have the patient try all 4 H1 blockers, one each week to see which one has the most benefit and least number of side effects. **Maximum/goal doses of H1 blockers:**  **Allegra**: 60 mg twice daily or 180 mg daily **Zyrtec**: 20 mg twice daily **Xyzal**: 10 mg twice daily **Claritin**: 20 mg twice daily **Maximum/goal doses of H2 blocker:** **Famotidine**: 20mg twice daily ## Mast Cell Stabilizers D-hist, by Ortho Molecular Products is an herbal mast cell stabilizing formula containing stinging nettle, Quercetin, and Bromelain. It is started at a loading dose of 2 capsules three times daily for 1-2 weeks. It can then be reduced to 3 capsules daily. Vitamin C has additional mast cell stabilizing effects and can be increased to 1,000 mg per day as tolerated. If additional support is needed, I have had good success with Gastrocrom which is a prescription strength mast cell stabilizer. ## Vagal Nerve Stimulation In addition to ruling out [[Cervical Instability]] as a cause for low vagal tone, vagal strengthening exercises such as relaxation exercises and Yoga Nidra can be helpful. Some people find vagal nerve stimulation moderately beneficial. ## Low Histamine Diet This diet cuts down on foods that are high in histamine or that trigger histamine release in the body. Some people will be more sensitive to some foods than others. I recommend an elimination diet where you cut out these histamine triggering and containing foods in a strict way and then slowly reintroduce them to see if you have a reaction. Remember that this effect is dose dependent. A small amount of edamame on a salad may not cause problems but a large serving of tofu will. If you have a histamine response, it will take 2-3 days for your mast cells to replenish their store of histamine. This is why you may become more sensitive to foods when you go on this diet (because your mast cells are not degranulating all the time, when they are triggered they will dump all of that histamine at once). A recent degranulation will also make it more difficult to detect foods that are triggering histamine release so you should not try reintroducing a new food for 3 days after a reaction. If you are really struggling with histamine issues, I recommend cutting out all of these foods at once to the best of your ability. If you struggle less, you can try eliminating one or a few at a time for about 4 weeks and then adding them back in (one at a time) to see if they cause you problems. > [!NOTE] This diet is second line > I have begun recommending the [[Fibro Food Formula]] before the low histamine diet because it cuts out many of the same foods but is not as difficult or complicated to maintain. High histamine foods can be added to the "yellow" food list in the Fibro Food Formula protocol. ## Foods to Avoid - Aged and fermented foods - Kombucha - Sauerkraut, kimchi, etc. - Wine, beer, alcohol - Aged/smoked meats (hot dogs, sausage, deli meat, jerky, etc.) - Aged cheese - Olives, pickles - Vinegar - Canned meat/fish - Dried fruit - Chocolate - Wheat and gluten (barley, rye) - Tomatoes - Eggplant - Soy and other legumes, especially if canned - Preserved and pre-prepared foods (do your best here) - Food additives (benzoate, sulphites, nitrites, glutamate, food dyes) - Certain fruits - citrus, kiwi, pineapple, papaya, strawberries, passionfruit, plum, banana - Certain nuts - peanuts, walnuts, cashews - Shellfish - Spinach - Squash - Milk and certain dairy products (it’s ok to have cottage cheese, cream cheese, ricotta cheese, mozzarella and ghee) If the patient is on a plant-based diet and relies on legumes for protein, consider eliminating soy but allowing other legumes into the "green" food category. # For Nose and Sinus Symptoms The best nasal spray for allergic rhinitis is Ryaltris which is a prescription combo antihistamine/steroid. Can also help with sinus headaches. # Sources 1. Afrin LB. Presentation, diagnosis, and management of mast cell activation syndrome. _Mast Cells_. Published online April 2013:155-232.