Mast cells release a variety of pro-inflammatory mediators when activated by an appropriate stimulus. These mediators include:

• Histamine: A potent vasodilator that increases vascular permeability and causes smooth muscle contraction.

• Proteases: Enzymes that break down proteins and can contribute to tissue damage.

• Prostanoids: Lipid-based molecules that have pro-inflammatory effects.

• Leukotrienes: Lipid-based molecules that can cause bronchoconstriction and increase vascular permeability.

• Heparin: A molecule that prevents blood clotting.

• Cytokines, chemokines, and growth factors: These molecules can regulate the functions of many organs and tissues.

Mast cells can be activated by many different antigens, including allergens, medications, infections, and insect or reptile venoms. When activated, they release these mediators in a phasic fashion.