What are allergies?

Allergies, sometimes referred to as allergic rhinitis, are a very common health problem involving an inappropriate response of our immune systems to allergens, substances that can induce allergic reactions. There are both outdoor and indoor allergens. Aside from different types of pollens and molds, allergens can include animal dander and dust mites.

Allergies can negatively impact quality of life, as well as decrease productivity in our daily jobs. Allergies can also worsen other health problems like asthma.
Maryanne R. Samuel, DO
Internal Medicine
Allergies occur when your immune system overreacts to a substance that is exposed to your body. While the substance is usually harmless, a slight irritation to your immune system causes it to react anyway.
Allergies, by definition, are a reaction to the body seeing something as "foreign." As a result, any part of your body that comes into direct contact with the environment around us or the things we breathe or ingest can cause an allergic reaction. Allergic symptoms include dry or itchy skin, hives, runny nose, or itchy, red eyes, shortness of breath, nausea, vomiting or diarrhea, or even swelling of your tongue or throat in more severe reactions.
Leigh Vinocur, MD
Emergency Medicine
Allergies are a result of overactive immune systems reacting to relatively harmless substances, such as dust and pollen, as they were invading bacterium or viruses.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
More than one-third of Americans have allergies, but most don't have their symptoms under control. Allergies are exaggerated reactions of the immune system to substances that don't cause symptoms in most people. Those reactions can come in the form of:

• Skin rashes (typically from chemicals)
• Runny and stuffy noses (from dust, pollen, etc.)
• Itchy eyes (from dust, pollen, etc.)
• Upset stomach or intestines (from food allergies)
• Coughing, shortness or breath, wheezing or any distress to the respiratory system (from any kind of allergen)
YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

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YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

Between your full-length mirror and high-school biology class, you probably think you know a lot about the human body. While it's true that we live in an age when we're as obsessed with our bodies as...

Allergies occur as a result of your immune system overreacting to a foreign substance. In an effort to protect your body, your immune system attacks foreign invaders and harmful substances. In some cases, however, your immune system mistakenly attacks a harmless substance, which produces an allergic reaction.

Picture of allergens
Jacob Teitelbaum
Integrative Medicine
Allergies occur when our body's immune (defense) system reacts to something harmless in our environment. Inhalation allergies like pollen can cause mild symptoms, such as red eyes, itching, hives or runny nose. Food allergies are more likely to cause a wide assortment of symptoms (fatigue, pain, nasal congestion, migraines, spastic colon, autism, and many more), and should be considered when your doctor does not know the cause of a problem. In rare cases they can be life threatening (anaphylaxis where the throat swells shut or shock can occur) as occurs in some peanut allergies. For those with the latter type, carrying an "Epi-pen" (preloaded adrenaline syringe) can be life saving.

Allergies occur when your body has an exaggerated response to a harmless substance (like dust) that it mistakenly perceives as an invader (like a virus). The immune system reacts by releasing antibodies to attack the harmless substance, known as an allergen. Antibodies trigger the release of histamine and other chemicals in the body that cause symptoms of allergies, such as itchy eyes, runny nose, nasal congestion, itchy skin, and hives.

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About one out of five Americans suffers from allergies. An allergy is an exaggerated response from the immune system to a substance such as dust, pollen, pet dander or mold. Other common triggers include foods such as peanuts and ...

milk; insect bites; and certain ingredients in cosmetics and jewelry. Allergies can cause anything from rashes and hives to itchy eyes, sneezing, coughing, diarrhea, vomiting, and wheezing.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.