Allergy symptoms occur when your body’s immune system overreacts to substances in your environment. Most people can live with a little cat dander, dust, or pollen, for example. But people with allergies have immune systems that can react to just about anything that comes along.

It fights these foreign substances just as it would bacteria or viruses, the main causes of run-of-the-mill are histamine and leukotrienes, biochemicals that your allergy symptoms immune system releases. Your immune system is an incredibly complex system of several different kinds of cells working in tandem. The overly sensitive cells involved in allergies are mainly mast cells and basophils.

Mast cells are found in tissues such as your skin, lungs, throat, stomach, and intestines, while basophils hang out in your blood vessels. As you can see, these cells monitor nearly every part of the body.