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Allergic reaction

Allergic reaction: Introduction

An allergic reaction is an over-response of the immune system to a particular substance or allergen (substances that cause an allergic reaction). Allergic reactions are common, and the severity of an allergic reaction can range from mild to severe to life-threatening. The most severe form of allergic reaction is an anaphylactic reaction. This type of allergic reaction is rare but rapidly becomes life-threatening and is a medical emergency.

There are a variety of types of allergies that cause allergic reactions. They include food allergies, respiratory allergies and skin allergies, which can result in such conditions as eczema and contact dermatitis.

In people who experience allergic reactions, the immune system is overzealous and reacts when they inhale, swallow or touch normally harmless substances, such as pollen or dust. The immune system is made up of special cells that circulate throughout the body to defend the body against foreign substances, such as viruses and bacteria. This over-reaction of the immune system during an allergic reaction results in the release of the chemical histamine. This causes the swelling, inflammation, and itching of tissues that are characteristic of an allergic reaction.

Almost any substance can cause an allergic reaction in a person who is sensitive to that particular substance. That substance is called an allergen. People who experience allergic reactions are often allergic to more than one substance. Common allergens include dust, pollen, mold spores, animal dander, bee stings, and cockroach or dust mite droppings. Other common allergic reactions occur in response to exposure to certain plants, such as poison ivy, and some medications, such aspirin or penicillin. Certain foods, such as eggs or milk, or chemicals and other substances, such as latex, are also common allergens that can cause an allergic reaction in a sensitive person.

When a person has an allergic reaction, exposure to an allergen can cause a wide variety of symptoms. Symptoms vary depending on the specific allergy, the type of exposure and the severity of the allergic reaction. Symptoms can affect the respiratory system, the skin and/or the gastrointestinal system. For more information on symptoms and complications, refer to symptoms of allergic reaction.

Making a diagnosis of an allergic reaction begins with performing a complete evaluation that includes a medical history, including symptoms, and a physical examination. Other tests may be done to rule out diseases or conditions with similar symptoms, such as an upper respiratory infection, sinusitis or other types of gastrointestinal diseases, such as irritable bowel syndrome.

Diagnostic testing may include skin patch testing. In a patch test, small amounts of common allergens are applied methodically to the skin to determine what substances are triggering an allergic reaction. A blood test called a radioallergosorbent test (RAST) may also be done to help identify the substance that is causing an allergic reaction. For suspected food allergies, a patient may also be asked to keep a food log to help determine the types of foods that trigger an allergic reaction.

It is possible that a diagnosis of an allergic reaction can be missed or delayed because symptoms can be similar to other conditions. For more information on misdiagnosis, refer to misdiagnosis of allergic reaction.

Patient compliance with a good treatment plan can control symptoms and repeat attacks of an allergic reaction to a degree that allows a person to live a normal, active life. Treatment may include a combination of lifestyle changes, medications, and other measures. For more information on treatment, refer to treatment of allergic reaction. ...more »

Allergic reaction: Normally, the immune system is the body's defense against invading agents such as bacteria and viruses. In most allergic reactions, however, ... more about Allergic reaction.

Allergic reaction: An acute reaction through exposure to a particular allergen. More detailed information about the symptoms, causes, and treatments of Allergic reaction is available below.

Allergic reaction: Symptoms

People who have an allergic reaction to a specific substance can experience a wide variety of symptoms that can affect the respiratory system, skin, gastrointestinal system, and in severe cases, the cardiovascular system. Symptoms can occur alone or in combination with other symptoms.

Common respiratory symptoms include sneezing, runny nose, nasal congestion, sinus pressure ...more symptoms »

Allergic reaction: Treatments

The most effective treatment plan for an allergic reaction uses a multifaceted approach. Treatment plans are also individualized to best address the specific cause and severity of the allergic reaction, and the patient's age and medical history. In general, allergies and allergic reactions are highly treatable, although they are generally not curable. On occasion ...more treatments »

Allergic reaction: Misdiagnosis

A diagnosis of an allergic reaction may be overlooked or delayed because symptoms may be mild in some people and/or may not occur very often. In addition, some symptoms, such as sneezing, runny nose, vomiting or diarrhea can mimic symptoms of other conditions. These include a cold, food poisoning, gastroenteritis, influenza, food intolerances, sinusitis, or eating too many ...more misdiagnosis »

Symptoms of Allergic reaction

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Allergic reaction: Related Patient Stories

Allergic reaction: Deaths

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Causes of Allergic reaction

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Allergic reaction: Undiagnosed Conditions

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Misdiagnosis and Allergic reaction

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Allergic reaction: Research Doctors & Specialists

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Allergic reaction: Rare Types

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Allergic reaction: Animations

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Article Excerpts about Allergic reaction

Normally, the immune system is the body's defense against invading agents such as bacteria and viruses. In most allergic reactions, however, the immune system is responding to a false alarm. When an allergic person first comes into contact with an allergen, the immune system treats the allergen as an invader and mobilizes to attack. The immune system does this by generating large amounts of one type of antibody. When the allergen and the antibody connect, it signals the release of powerful inflammatory chemicals. These chemicals, like histamines, cytokines, and leukotrienes, act on the tissues of various parts of the body, such as the respiratory system. The result is the symptoms commonly associated with allergies. (Source: excerpt from Allergies: NWHIC)


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