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Medical and Healthy Living Glossary - I

This page of our online glossary of medical and healthy living is for medical and healthy living terms beginning with the letter 'I'.

Ibuprofen - A nonsteroidal anti-inflammatory drug which relieves pain and swelling, especially in arthritis and rheumatism. It is also widely used as a household painkiller.
Illegal Residue - The presence of a pesticide or other substance at harvest in excess of the tolerance level.
Immune - Being protected against an infection by the presence of antibodies specific to the organism concerned.
Immune Compromised - Person with a weakened immune system.
Immune System - A complex network of cells and cell products, which protects the body from disease. The immune system includes the thymus, spleen, lymph nodes, white blood cells and antibodies.
Immunity - The ability of the body to resist infection because of the presence of antibodies and white blood cells. Antibodies are generated in response to the presence of antigens of a disease. There are several types of immunity: active immunity is when the body produces antibodies and continues to be able to do so during the course of a disease, whether occurring naturally (also called acquired immunity) or by deliberate stimulation. Passive immunity is short-lived and is provided by the injection of ready-made antibodies from someone who is already immune.
Immunization - Immunity to disease by artificial means. Injection of an antiserum will produce temporary passive immunity, while active immunity is produced by making the body generate its own antibodies. This is done by the use of treated antigens (vaccination or inoculation). Vaccine is used for immunization, and it may be derived from live bacteria, viruses or dead organisms and their products.
Immunoglobulins - A group of high molecular weight proteins that act as antibodies and are present in serum and secretions. There are five main groups, each with different functions. Immunoglobulin A (Ig A) is the most common and occurs in all secretions of the body. It is the main anti-body in the mucous membrane of the intestines, bronchi, saliva and tears. Ig A defends the body against micro-organisms by combining with a protein in the mucosa. Ig D is found in the serum in small amounts but increases during allergic reaction. Ig E is found primarily in the lungs, skin and mucous membrane cells and is an anaphylactic antibody. Ig G is synthesized to combat bacteria and viruses in the body. Ig M or macroglobulin has a very high molecular weight (about five or six times that of the others) and is the first produced by the body when antigens occur. It is also the main antibody in blood group incompatibilities.
Immunosuppression - The use of drugs (immuno-suppressives) to suppress the body's natural immune system so that it will not reject a transplanted organ. These drugs are used to maintain the survival of the transplanted organs in transplant surgery and to treat autoimmune diseases. The condition may also be produced as a side effect, for example, after chemotherapy treatment for cancer. In all instances, there is an increased risk of infection.
Immunotherapy - A still largely experimental technique of developing the body's immunity to a disease by administering drugs or gradually increasing doses of the appropriate allergens, thereby modifying the immune response. The most widely studied disease is cancer, where immunotherapy forms an auxiliary treatment to drug therapy.
Incubation Period - Length of time it takes for a virus or bacterium to develop in the body after contamination or infection, before the appearance of the symptoms of the disease.
Indoles - Nitrogen compounds found in Brussels sprouts and other members of the cruciferous or cabbage family. Vegetable indoles are thought to speed up the elimination of the female hormone oestrogen from the body, and therefore may help to protect against hormone-related cancers, such as cancer of the womb and breast cancer.
Irradiation - Treatment of food with low doses of radiation to kill or inactivate microorganisms.
Irritable Bowel Syndrome - A condition caused by abnormal muscular contractions (or increased motility) in the colon, producing effects in the large and small intestines. Symptoms include pain in the abdomen, which changes location, disturbed bowel movements with diarrhoea then normal movements or constiption, heartburn and a bloated feeling caused by wind. The specific cause is unknown and no disease is present. Treatment is limited to relief of anxiety or stress (which may be contributory factors), drug therapy to reduce muscle activity, and careful choice of diet to include a high fibre content.
Insoluble Fibre - The fibre in bread and cereals that passes unchanged through the intestines because it cannot be absorbed or broken down by the body's own enzymes. Insoluble fibre is however fermented by bacteria in the large or lower intestine, producing the beneficial short chain fatty acids.
Insulin - A hormone produced by the islets of Langerhans in the pancreas that prevents excessive levels of glucose from accumulating in the blood, by enabling its uptake by cells. In diabetes mellitus, the most common form of diabetes, the body does not produce enough insulin, and so blood sugar levels can rise unchecked, with potentially fatal consequences. Insulin injections are regularly used to treat diabetes mellitus.
Isothiocyanates - Plant chemicals which are believed to strengthen the body's defence against some forms of cancer. Isothiocyanates occur naturally in some cruciferous vegetables such as broccoli, Brussels sprouts and cabbage.