So far you have learned about some allergy facts and what are allergies. But to undestand what is responsible for the allergy symptoms like runny nose, itchy eyes etc, you need to have an understanding of mast cells. So what are mast cells? A mast cell is a type of immune cell from bone marrow and initially was thought to be helpful as mast is derived from a German word that means food and it was believed that mast cells would nourish tissues. Today, mast cells are now known to be present in most tissues such as: blood vessels and nerves, skin tissue lining the lungs, the digestive tract, and mouth tissues surrounding the eyes and nose.
When stimulated by an allergen, mast cells will release chemicals such as histamine, prostaglandins and leukotrienes that result in allergy/asthma symptoms. The symptoms will vary depending on where the mast cell is located. If the mast cell is located on the nose and is stimulated, then you might develop sinus congestion. If the mast cell is located on the skin and stimulated, then you might develop a skin rash. If the mast cell is located on the bronchial tubes and stimulated, then you might develop asthma. If the mast cell is located on the intestinal tract and stimulated, then you might develop diarrhea and an upset stomach.