Food Allergies

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Introduction

Many people have food intolerances, such as lactose intolerance with milk, but true food allergies only affect about 1% of all people.  Food allergies are more common in children, and some children outgrow them.  People with food allergies should avoid the foods that they are allergic to and receive immunotherapy shots from an allergist.  Life threatening allergic reactions require emergency medical treatment.
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Anatomy

Your immune system usually fights germs to keep you healthy.  If you have allergies, your immune system overreacts to ordinary substances that normally are not harmful.  The substances that trigger an allergic reaction are called allergens.

When you are exposed to an allergen, your white blood cells produce antibodies.  The antibodies trigger the release of histamine and other chemicals in your blood called mediators.  The mediators cause the symptoms of the allergic reaction.
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Causes

Infants and young children tend to have more allergic reactions to milk, eggs, and peanuts.  Some children may outgrow childhood food allergies.  The most common foods that cause allergic reactions are:

• Eggs
• Milk
• Peanuts, peanut products such as peanut butter
• Tree nuts, such as walnuts, pecans, almonds, cashews
• Shellfish, such as shrimp, lobster, crab
• Soy nuts or soy products
• Wheat
• Fish
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Symptoms

Symptoms of food allergy appear immediately or within a few hours of eating.  The primary symptoms of food allergies are wheezing, hives, and a hoarse voice.  You may experience difficulty swallowing, difficulty breathing, nausea, vomiting, diarrhea, abdominal pain, itching, light-headedness, fainting, nasal congestion, and runny nose.  Your eyelids, tongue, and lips may swell.  Your throat, tongue, mouth, or skin may itch.

A potentially life threatening reaction, anaphylaxis, requires immediate medical treatment.  Symptoms of anaphylaxis include hives, itching and pale or flushed (reddened) skin.  It can be difficult to breathe if the airways narrow and the throat and tongue swell. A wheezing noise may be heard while breathing.  The pulse may feel weak and fast.  Nausea, vomiting, diarrhea, dizziness, and fainting can also occur.

A severe anaphylaxis reaction can cause a person to develop anaphylactic shock and stop breathing or stop the heart.  Symptoms of anaphylactic shock include a sudden drop in blood pressure, difficulty breathing, and a loss of consciousness.  Again, immediate emergency medical treatment is needed.  In some cases death can result.
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Diagnosis

If you are experiencing life threatening symptoms, you should  receive emergency medical treatment.  If you experience mild symptoms, you should contact your doctor.  A blood test or skin test can confirm your allergy.
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Treatment

Again, if you are experiencing severe symptoms, call 911.  If you have a mild reaction, your doctor may prescribe antihistamine medication to relieve your symptoms.  An emergency shot of epinephrine (EpiPen, EpiPen Jr., Twinject) may be recommended for you to use the next time you have an allergic food reaction.  You should still seek emergency medical treatment if you use the shot.

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Prevention

You should avoid the foods to which you are allergic.  Read food labels carefully, and ask questions about ingredients when dining out.  Infants that are breastfed may have a reduced risk of food allergies.

Wear a medical alert ID bracelet or necklace.  Inform your family, co-workers, and others around you that you have a particular food allergy.  Carry your emergency shot with you at all times.  Instruct those around you how to give you the emergency shot in the event that you are unable to give it to yourself.
 
An allergist can test you for food allergies and provide preventive immunotherapy shots.
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Am I at Risk

You are at risk for food allergies if you eat foods to which you are allergic.  Note that both raw and cooked food can cause food allergies.
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Complications

A potentially life threatening anaphylaxis reaction can result from a food allergy.  Although it is uncommon, death can occur.
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This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

The iHealthSpot patient education library was written collaboratively by the iHealthSpot editorial team which includes Senior Medical Authors Dr. Mary Car-Blanchard, OTD/OTR/L and Valerie K. Clark, and the following editorial advisors: Steve Meadows, MD, Ernie F. Soto, DDS, Ronald J. Glatzer, MD, Jonathan Rosenberg, MD, Christopher M. Nolte, MD, David Applebaum, MD, Jonathan M. Tarrash, MD, and Paula Soto, RN/BSN. This content complies with the HONcode standard for trustworthy health information. The library commenced development on September 1, 2005 with the latest update/addition on February 16, 2022. For information on iHealthSpot’s other services including medical website design, visit www.iHealthSpot.com.