Science & Technology in Action

3rd Edition

What Causes Allergies?

Teva Ireland

The common factor in allergies is the inflammatory response to substances that are not generally harmful.
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Lesson excerpt

Allergy means ‘altered reaction’ – it is the inappropriate and harmful response of the body’s defence mechanisms to substances that are normally harmless. It can be an attack of sneezing and runny eyes (hay fever), an itchy red rash (eczema), wheezing when breathing (asthma) or swelling of lips and tongue and vomiting (food allergy). Allergies affect about a third of the population.

What is the inflammatory response?
Our immune system protects us against disease. If we get a cut it may become red and swollen. This inflammatory response is part of our general defence system. The tissues that are exposed to the environment (skin, gut lining, mouth, nose and lungs) have special cells, called mast cells, which release chemicals, including histamines, when the tissues are damaged. These substances cause the walls of blood capillaries to become more porous and white blood cells and blood proteins, which are needed for clotting and sealing wounds, can move out of the blood. Within an hour the area is teeming with white blood cells (monocytes, also called phagocytes), which engulf any foreign particles and clear the area for repair.

What is induced immunity?
The specific immune system or adaptive immune system, is specific to vertebrates, and is particularly effective against dangers to which we have previously been exposed. It consists of white blood cells called lymphocytes, of which there are two main types – B cells and T cells. They are both made in bone marrow but B lymphocytes mature in bone marrow and T lymphocytes mature in the thymus gland. Antigens are foreign molecules often on the surface of bacteria or viruses that trigger the immune response of the lymphocytes. 

True or False?

  1. T-lymphocytes produce antibodies false
  2. An antigen is a foreign molecule that stimulates the production of antibodies true
  3. Swelling and redness at a cut are examples of the inflammatory response true
  4. B-cells mature in the bone marrow true
  5. The general defence system protects the body by producing antibodies false
  6. Antibodies are part of the group of biomolecules known as carbohydrates false
  7. Mast cells release histamine which is responsible for hypersensitivity responses true
  8. Inability to breath properly in asthma is due to expansion of blood vessels, making airways narrower false
  9. Phagocytes kill foreign bodies by engulfing them true
  10. Exposing a person to an allergen resulting in histamine production by mast cells is known as immunisation false