What Is an Allergen?

An allergen is a food or other substance that causes an allergic reaction in a person.

For example, if you have a food allergy, eating a particular food that you are allergic to will cause allergic symptoms. These can range from a runny nose to hives to a more serious allergic reaction called anaphylaxis, which requires emergency medical attention.

Common types of allergens

Allergens are present in the environment as well. For instance, both pollen and dust enter the body by being inhaled. They can cause allergic reactions such as a runny nose, headache, sinus pressure, and sneezing. According to the American Academy of Allergy Asthma & Immunology (AAAAI), almost 8 percent of the U.S. population over 18 years of age suffer from hay fever. Interestingly, the AAAAI also reports that about 8 percent of children in the U.S. have some kind of food allergy. Peanut is the most prevalent food allergen, causing a peanut allergy reaction in some people. Milk is the next prevalent allergy with shellfish next in line.

Some other common allergens include animal dander, dust, perfumes, plants, smoke pollen, drugs such as antibiotics, chemicals, and bacteria and viruses. Scientists are not sure why allergic diseases are rising in the industrial world, but according to AAAAI, they have been increasing for over 50 years. In addition, 40 to 50 percent of school children around the world are allergic to one or more common allergens. It is not known why some people have allergic reactions to allergens while other people are not affected by them.

What does an allergen do to the body?

Allergens are substances that can cause serious reactions or even death. A person's immune system believes that the allergen is a foreign substance that will cause a problem for the person. Knowing this, the immune system steps into action by trying to rid the body of the substance. Your brain immediately tells your immune system to release antibodies that are ready to fight the allergen. Histamine is released to fight off the subject causing the allergic reaction. The symptoms that you have during an allergy attack are the body's way of trying to force the allergen out of your system. For instance, when you sneeze, have runny eyes and a runny nose, this is your body's attempt to get the allergen out of your nose and eyes.

Once you have had an allergic reaction to an allergen, you have antibodies against this substance in your blood. When an allergist performs an allergen-specific IgE antibody test, it is used to find out if a patient is allergic to a certain substance. This type of test is particularly helpful when a person has allergic symptoms that are ongoing. Blood tests are often used to identify food allergies as well as environmental allergies.