Mast cells are a type of immune cell that originates in the bone marrow and are found in most tissues. They play a role in both health and disease, and are most commonly known for their role in atopic disorders (allergies) and anaphylaxis. When they’re functioning normally, mast cells release chemicals that help protect the body—they’re like first responders for the immune system. But when they’re not properly regulated, mast cells can degranulate and dump their chemical mediators too easily, causing havoc across the body in a condition called mast cell activation syndrome (MCAS). Mast cells have been linked to several chronic allergic/inflammatory disorders, autoimmune diseases, and cancers. Some people with MCAS develop a histamine intolerance.
If someone has mast cell activation syndrome, the mast cells overreact and release chemicals when they shouldn’t. Often, they erroneously see food, fragrances, temperature, and even stress as something to “defend against.” Depending on which chemical the mast cells release, people can experience a whole range of symptoms, including hives, diarrhea, shortness of breath, anxiety, fatigue, brain fog, congestion, lightheadedness, and much more. MCAS may even cause anaphylaxis, a medical emergency. It may pop up in people who have Ehlers-Danlos Syndrome (EDS), a connective tissue disorder, Postural Orthostatic Tachycardia Syndrome (POTS), myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), long COVID, or Lyme disease, among others.
MCAS is difficult to diagnose and treatment response varies. Finding the root cause or trigger is key. If someone has MCAS, it is important to identify and avoid substances and environments that provoke the symptoms. If a severe anaphylactic reaction occurs, call 911 right away—emergency treatment will be needed with epinephrine. Natural and pharmaceutical antihistamines, mast cell stabilizers, and supplements can help. Steroids are also used to help treat the symptoms.
The mast cells are just trying to do their job and keep the body safe, but as is often the case, the immune system can lose its natural checks and balances and may need help getting back on track.