What are Mast Cells?

Mast cells (MC) are immune system cells that live in the bone marrow and in body tissues, internal and external, such as the gastrointestinal tract, the lining of the airway, and the skin. Everyone has mast cells in their body, and they play many complex and critical roles in keeping us healthy. The positive roles that they play include protecting us from infection, and helping our body by participating in the inflammatory process. However, mast cells are also involved in allergic reactions, from the tiny swelling that appears after a mosquito bite to a life-threatening, full-blown anaphylaxis.

Mast cells have within them small sacs, or granules, surrounded by membranes (Figure1). The sacs contain many different kinds of substances called mediators, which participate in all of the roles above, including allergic response and anaphylaxis. 

The mediators are selectively released when there is an allergic or mast cell based reaction.¹

There is a difference between someone who is healthy, with mast cells that are functioning normally, and someone with a mast cell disease, whose mast cells may be activating inappropriately in response to triggers or may also be proliferating and accumulating in organ tissues.