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    Understanding Allergies -- the Basics

    What Are Allergies?

    Allergies are a reaction by your immune system to something that is usually not harmful. Allergies come in a variety of forms and can be anywhere from mildly bothersome to life-threatening. About 17 million adults and 7 million children in the U.S. have an allergy.

    Right now, researchers aren’t sure why people get allergies, but genes appear to play a role. Allergies may flare up and subside throughout your life.

    Understanding Allergies

    Find out more about allergies:

    Basics

    Symptoms

    Treatment

    Prevention

    Your immune system protects your body from foreign substances, known as antigens, by making antibodies and other things to fight them. Usually it ignores harmless substances, like food, and fights the dangerous ones, like bacteria.

    An allergic reaction happens when your immune system attacks something harmless as if it were a threat. These harmless things are called allergens. Your body creates a chemical called histamine, which causes many of the symptoms that go with allergies. Things that can trigger an allergy attack range from pollen to pet dander to penicillin.

    Most reactions aren’t serious, but some, like anaphylaxis, can be fatal. It can make you stop breathing or send your blood pressure to too low. Allergies can't be cured, but there are lots of treatments to relieve the symptoms. If you have a severe allergy, see a doctor and get it treated.

    Types of Allergies

    Allergic  Skin  Conditions

    Hives, or urticaria, is a rash with itchy, swollen, reddened sores that can last for minutes or days. Sometimes they come with angioedema, a deeper swelling under your skin. It most often shows up around your eyes and lips, but sometimes it can affect your hands, feet, or other body parts.  

    Causes include foods, pollen, animal dander, drugs, insect stings, cold, heat, light, or even emotional stress. Often, you don’t know what caused them. If you have hives or angioedema that won’t go away, tell your doctor.

    Eczema, also known as atopic dermatitis, is a skin condition sometimes triggered by allergies. Avoiding your allergy triggers can help you avoid flare-ups of eczema.

    Respiratory Allergies

    As many as 50 million Americans have hay fever. Your doctor may call it allergic rhinitis. It can cause inflammation in your sinuses, or sinusitis. Typical symptoms include itchy eyes, nose, roof of mouth, or throat, along with nasal congestion, coughing, and sneezing. If you (or members of your family) have other allergic conditions like eczema or asthma, you’re more likely to get hay fever

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