The body has many barriers to infection and various types of immune response to invading organisms and cancerous cells. For example, sebum and sweat, excreted by the skin, are mildly antiseptic. Tears contain a more powerful antiseptic. Mucus, secreted by the lining of the respiratory tract and the stomach, protects the body by trapping harmful organisms. In the antibody immune response, white blood cells known as B lymphocytes or B cells attack and destroy invading bacteria. In the cellular immune response, white blood cells known as T lymphocytes or T cells attack and destroy viruses, parasites and cancer cells.
In an allergic reaction, the immune system becomes sensitized to a substance that is normally harmless, such as pollen. Subsequent exposure to the substance causes mast cells, which are located in the skin and nasal lining as well as in other tissues, to be destroyed, releasing histamine. Histamine causes an inflammatory response and brings on the symptoms of allergy.
THE ATOPIC FAMILY OF CONDITIONS
I’d like to tell you about a particular and common form of allergy. What is atopy? The word “atopic” means that a person is born with an extra sensitivity to certain things, usually invisible proteins called allergens, in the environment. The commonest triggers or allergens in these people are the house dust mite (more accurately the droppings of house dust mite), grass, tree and weed pollen, proteins on cat and dog fur, feathers and occasionally foods, such as egg, milk or nuts.
Atopic people have a hypersensitivity of their immune system and produce too much of the IgE allergy antibody. They have no other problem with their immune system, but this sensitivity leads to ATOPY A gene is responsible and the gene can be passed down through a family. Family members show up this atopic
gene in any or all of several different ways.
So if you belong to an “atopic” family you’ll be able to track your “atopic” gene showing up as any of these conditions:
- childhood eczema
- adult dermatitis
- childhood asthma
- hay fever
At first glance these conditions don’t seem to be closely related, but they’re all expressions of the atopic gene so I describe them here as a family of conditions.