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Asthma, allergies and eczema usually run in the family. If you have all three of these diseases, we will sometimes refer to you as an “atopic individual”. However, all three diseases are different. Approximately one-third of the people who have allergies also have asthma problems, and about one-third of those also have eczema problems.
If you check your family history for two or three generations back, some family members may have just had allergies, some of them may have had both allergies and asthma, and some may have had all three. Allergic tendencies run in families. Once a person has a tendency, he must be exposed to potential allergens for awhile. The greater the exposure, the greater the chance of developing allergies. Once a person has been exposed to a potential allergen long enough, his or her immune system produces a specific IgE antibody to that allergen.
Normally, we all make antibodies which belong to the classes of immunoglobulin A, G, and M, which we need for protection from infections. However, the IgE response is an abnormal response which actually causes the allergic reactions. The IgE antibodies are very specific to each antigen. For example, if you are allergic to cats, you make an IgE antibody very specific to cat proteins. Once these IgE antibodies are made, they affix to the surface of a mast cell. The mast cells are located in the nasal linings, conjunctivae, lungs, GI tract, and skin. These mast cells are loaded with histamine and other inflammatory chemicals. Once there is re-exposure to the antigen, all these chemicals are released and together create an inflammation.
Inflammation in the nose is called rhinitis. Inflammation in the eyes is called conjunctivitis, and if there is a tendency for asthma, inflammation in the airways within the lungs causes asthma. If a sensitive person is exposed to a food allergen, he or she can develop hives and angioedema with swelling of the lips and throat, wheezing, or anaphylaxis.
When we do skin testing, we put the antigen on the surface of the skin, and if the person has an IgE antibody that that antigen, a small local reaction, redness and swelling at the site of the skin test occurs.
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