When you come across your allergy trigger, your immune system knows and sends a chemical signal to “mast cells”. This is a type of white cell that is found in connective tissues all through the body, especially under the skin, near blood vessels and lymph vessels, in nerves, and in the lungs and intestines, to release histamines.

When Histamines leave the mast cells, they boost blood flow in the area of your body the allergen affected. This causes inflammation, which lets other chemicals from your immune system step in to do repair work. Histamines then land on their own receptors in your body. The results of it might cause you to have a runny or stuffy nose, coughing, itchy eyes, and nose. If you have a food allergy, you may experience hives, itchy or flushed skin, red eyes, facial swelling, headaches, asthma attacks, or constipation.