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Mast cells are a normal part of the immune system. They live in the bone marrow, flow through the bloodstream, and are located in every organ and connective tissue of the body. When these cells detect stress, injury, toxins, or infection, they release specific chemicals (mediators) that trigger an immune response. Mediators cause inflammation, which helps the body heal from an injury or infection. Mast cell activation syndrome (MCAS) occurs when the mast cells in the body release too much of the mediators at the wrong times. 


Too many mediators can cause symptoms in every system in your body. The most commonly affected areas include the skin, nervous system, heart, and gastrointestinal tract. Symptoms experienced in different parts of the body include:

  • Skin: itching, flushing, hives, and sweating
  • Nose: itching, running, and sneezing
  • Mouth and throat: itching, swelling of the tongue, lips, or throat
  • Lungs: trouble breathing and breezing
  • Eyes: itching and watering
  • Heart and blood vessels: low blood pressure and rapid heart rate
  • Nervous system: headache, dizziness, confusion, and extreme tiredness


There are no known causes of MCAS, but the condition appears to be inherited in some cases. Symptoms of MCAS are caused by excessive chemical mediators inappropriately released by mast cells. Potential triggers of MCAS include:

  • Allergic-type triggers
  • Drug-induced triggers
  • Stress-related triggers
  • Smells, such as perfume
  • Hormonal changes
  • Mast cell hyperplasia, a rare condition that can occur with some cancers and chronic infections


There is no cure for MCAS, but there are ways to manage your symptoms. If allergies trigger a person’s symptoms, they can often treat the symptoms themself with antihistamines and try to reduce exposure to that allergen. Other treatments include:

  • H1 or H2 antihistamines
  • Corticosteroids
  • Mast cell stabilizers
  • Antileukotrienes
  • Immunotherapy 
  • Epinephrine for more severe symptoms, such as anaphylactic shock

With allergy skin testing, patch testing, and/or blood testing, we can discover hidden triggers, confirm suspected triggers, and provide additional treatments, including advanced testing for mast cell activation syndrome. Contact Northeast Allergy, Asthma & Immunology today to schedule your appointment.

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