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.
Certain medical conditions such as sinus problems, eczema, and asthma are linked to allergies.
Allergy to mold - animal 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.Reviewer: 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: 01/07/2009
Anaphylaxis (8 images)
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(Doctor-Reviewed information)
Anaphylaxis is a life-threatening type of allergic reaction.Anaphylactic reaction; Anaphylactic shock; Shock- anaphylactic.Anaphylaxis is an severe, whole-body allergic reaction. After being exposed to a substance like bee sting venom, the person''...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, mostly in the nose and eyes, which occur when you breathe in something you are allergic to, such as dust, dander, or pollen.When these symptoms are caused by plant pollen, the allergic rhinitis is com...Reviewer: 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: 01/09/2009
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.Normally, your body''s immune system defends against potentially harmful substances, such as bacteria, viruses, and toxins. In some peopl...Reviewer: 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: 04/23/2009
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.When you have an allergic reaction to a substance, your body releases histamine and other chemicals into your bloodstream. Reviewer: Kevin Berman, MD, PhD, Associate, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network.Date: 04/15/2009
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.Allergic reactions are common. The immune response that causes an allergic reaction is simila...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).Adverse reactions to drugs are common, and almost any drug can cause an adverse reaction. Reactions range from irritating or mild side effects such as nausea ...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: 08/06/2008
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.Patch tests- allergy; Scratch tests- allergy; Skin tests- allergy; RAST test.There are many methods of allergy testing. Among the more common are...Reviewer: 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: 01/09/2009
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