Everything you need to know about allergies

A substance that causes an allergic reaction is called an allergen. Many allergens are everyday substances that are harmless to most people. However, anything can be an allergen if the immune system has a specific type of adverse reaction to it.

One of the roles of the immune system is to destroy harmful substances in the body. If a person has an allergy to a substance, their immune system will react as though that substance is harmful and will try to destroy it.

Causes

When an allergic reaction occurs, allergens bind to antibodies that the body produces called immunoglobin E (IgE). Antibodies combat foreign and potentially harmful substances in the body. Once the allergen binds to IgE, specific types of cells — including mast cells — will release chemicals that trigger the symptoms of the allergic reaction. Histamine is one of these chemicals. It causes the muscles in the airways and walls of the blood vessels to tighten. It also instructs the lining of the nose to produce more mucus.

Risk factors

People may have a higher risk of allergies if they are under 18 years old or have a personal or family history of asthma or allergies. Some researchersTrusted Source have suggested that those born by cesarean delivery may also have a higher risk of allergies, as they do not have exposure to the mother’s microbiome during childbirth.