Knowledge Base

What is an allergy?

Allergies are adverse reactions from the body to a normally harmless substance which affects one in four people in the UK (M.L.Levy, 2004).The reaction comes specifically from the immune system, usually responsible for fighting viruses and germs. The reasons for the rise in isn’t well understood, however, we believe that it could be down to our cleaner environments, which is reducing what our immune systems are exposed to, causing them to overreact to harmless substances.


The usual way the immune system works is to attack harmful viruses or bacteria, such as Salmonella or Staphylococcus aureus, when they enter the body. Trillions of white blood cells make up an important part of our immune system and travel around the body to detect anything harmful. When they detect what is believed to be a harmful substance, the white blood cells will direct the production of immunoglobulin, which is a protein also known as an antibody. Immunoglobulin will then bind to the harmful substance, such as viruses or bacteria, to make it harmless. Antibodies are extremely unique. Each harmful substance requires a different antibody to fight it. Trying to fight a flu virus with an antibody for Salmonella simply won’t work. So, each time a new substance enters the body, new specific antibodies are produced by the body to fight it.


In people who have allergies, the body works exactly as it should for fighting viruses and bacteria. However, it also responds to harmless substances as though they were attackers. When this happens, the immune system becomes sensitive to the substance and produces antibodies against it, which programs the immune system to react to whenever the substance enters the body. This is known as an allergic reaction. During an allergic reaction, the white blood cells send chemical messages around the body, jolting every part of the immune system into action. Common cells of the immune system are called mast cells. These are mostly found in the airways of the lungs, the eyes, nose, and throat. They hold antibodies on their surface. When an allergen is detected, these cells release chemicals which enlarge the blood vessels, contract the muscles in the lung airways, and trigger the production of mucus to defend the body.


These rapid changes can cause swelling and soreness, which in turn causes coughing, a runny nose, and itching in the mouth. It can also involve the skin causing rashes and itching.


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