Mast Cells (Allergy Alarm Cells)

Guards packed with grains

Mast cells start out in your bone marrow. Then they travel out and settle in places that touch the outside world, like your skin, nose, lungs, and gut.

They often sit next to blood tubes. Each mast cell is stuffed with grains full of alarm chemicals, like histamine.

Itchy, sneezy alarms

• When a mast cell senses germs, it releases its alarm chemicals.
• Histamine makes nearby blood tubes leaky so helper cells can rush in.
• In an allergy, mast cells react to harmless things like pollen or pet hair. That causes sneezing, a runny nose, or itchy skin.

Allergy medicine called an antihistamine works by blocking histamine.

Mast cell quiz