Mast cells

Mast cells are immune cells stationed in skin, airways, gut and around blood vessels that store histamine and release it during allergic and inflammatory responses.

They originate in bone marrow, migrate into tissues and mature there, living for months near the surfaces where the body meets the outside world. Their surface carries receptors for IgE, the antibody class linked to allergy, so an allergen that binds those antibodies triggers degranulation. Mast cells also respond to bacteria, venom, physical stimuli and nerve signals, and they release cytokines and growth factors that recruit other immune cells and support wound healing, so their role extends well beyond allergy.

Too many mast cells, or mast cells that activate too readily, underlie conditions such as mastocytosis and mast cell activation syndrome, which are assessed with blood tryptase, urine mediator tests and sometimes tissue biopsy. Mast cells express CB1 and CB2 receptors, and laboratory research has examined how cannabinoids, including CBD, influence their activation, with limited and sometimes inconsistent findings.