Allergies are relatively common. Both genetics and environmental factors play a role.
Allergy is caused by an oversensitive immune system, which leads to a misdirected immune response. The immune system normally protects the body against harmful substances, such as bacteria and viruses. It reacts to substances (allergens) that are generally harmless and in most people do not cause a problem.
But in a person with allergies, the immune response is oversensitive. When it recognizes an allergen, it releases chemicals, such as histamines. This causes itching, swelling, mucus production, muscle spasms, hives, rashes, and other symptoms, which vary from person to person.
What part of the body is contacted by the allergen plays a role in the symptoms you develop. For example, allergens that are breathed in often cause a stuffy nose, itchy nose and throat, mucus production, cough, or wheezing. A food allergen can cause nausea, vomiting, abdominal pain, cramping, diarrhea, or a severe, life-threatening reaction. Allergies to plants often cause a skin rash. Drug allergies usually involve the whole body and can lead to a variety of symptoms.
Some medical conditions, such as eczema and asthma, are linked to allergies.
Allergy to mold - dander - dust (4 images)(Doctor-Reviewed information)
Allergy-related symptoms can occur after you are around mold, certain animals or animal hair, dust, and other substances. These substances are usually found indoors and do not cause symptoms for most people. See also: Asthma; Allergic rhinitis. Reviewer: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.Date: 10/30/2006
Anaphylaxis (8 images)
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(Doctor-Reviewed information)
Anaphylaxis is a life-threatening type of allergic reaction. Reviewer: David C. Dugdale, III., MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 04/28/2008
Allergic rhinitis (3 images)
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(Doctor-Reviewed information)
Allergic rhinitis is a collection of symptoms, predominantly in the nose and eyes, caused by airborne particles of dust, dander, or plant pollens in people who are allergic to these substances. When these symptoms are caused by pollen, the allergic rhinitis is commonly called hay fever. See also: Allergies; Allergy to mold, dander, dust; Asthma. Reviewer: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.Date: 10/30/2006
Food allergy (6 images)(Doctor-Reviewed information)
A food allergy is an exaggerated immune response triggered by eggs, peanuts, milk, or some other specific food. Reviewer: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.Date: 07/25/2007
Hives (10 images)(Doctor-Reviewed information)
Hives are raised, often itchy, red welts on the surface of the skin. They are usually an allergic reaction to food or medicine. Reviewer: Kevin Berman, MD, PhD, Associate, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network.Date: 04/12/2007
Allergic reactions (10 images)(Doctor-Reviewed information)
Allergic reactions are sensitivities to substances, called allergens, that are contacted through the skin, inhaled into the lungs, swallowed, or injected. Reviewer: David C. Dugdale, III., MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 04/28/2008
Drug allergies (11 images)(Doctor-Reviewed information)
Drug allergies are a group of symptoms caused by allergic reaction to a drug (medication. Reviewer: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.Date: 07/19/2007
Allergy testing (4 images)(Doctor-Reviewed information)
Allergy tests are any of several tests used to determine the substances to which a person is allergic. Reviewer: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.Date: 07/17/2007
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