Food Allergies

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What are food allergies?

Food allergies are a disorder resulting in an immune system reaction after eating a certain food, producing symptoms such as skin rashes or digestive problems. Symptoms of food allergies are caused by the release of the body’s antibodies to protect itself from the food (allergen), which it mistakenly perceives as a danger or threat. In some cases, this response can be a severe or even a life-threatening reaction known as anaphylaxis.

Food allergies affect approximately 2% of adults and 6% of children in the United States. Ninety percent of all food allergies are caused by eight foods: eggs, fish, wheat, milk, peanuts, shellfish, soy, and tree nuts (Source: FamilyDoctor.org).

Food allergies typically cause mild symptoms during the first exposure to the food because the body uses this exposure to prepare the immune system reaction for a second exposure. If the subsequent response is severe, anaphylaxis, a severe life-threatening immune reaction, may ensue, requiring immediate medical attention. Food allergies can occur even if only a minute amount of the food is consumed.

The signs and symptoms of antibody-mediated food allergies can appear within a few minutes or up to 2 hours after eating the offending food. The disease course varies among individuals. Some people with food allergies have mild symptoms, such as a skin rash. Others may have severe diarrhea, swelling of the throat, or tightening in the lungs, causing difficulty breathing, which may be life threatening.

In some people, food allergies can trigger a severe allergic reaction called anaphylaxis. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms, including severe difficulty breathing, which may be combined with rapid heart rate (tachycardia); confusion or loss of consciousness even for a brief moment; or sudden swelling of the lips, face or throat.

What are the symptoms of food allergies?

Food allergies are caused when your body’s immune system produces an inflammatory reaction to the ingestion of food. This reaction commonly occurs after the second exposure to the food. Symptoms of food allergies occur between several minutes to a few hours after ingestion of the food. The nature of the symptoms and their intensity vary among individuals.

Common symptoms of food allergies

You may experience food allergy symptoms if you consume any food to which you are allergic. At times any of these food allergy symptoms can be severe:

Serious symptoms that might indicate a life-threatening condition

In some cases, food allergies can be life threatening. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

  • Airway tightening and constriction

  • Change in level of consciousness or alertness, such as passing out or unresponsiveness

  • Rapid heart rate (tachycardia)

  • Respiratory or breathing problems such as shortness of breath, difficulty breathing, labored breathing, wheezing, not breathing, or choking

  • Sudden swelling of the lips, face, tongue, or throat

What causes food allergies?

Food allergies are caused by the immune system activating cells to release antibodies known as immunoglobulin E (IgE) antibodies. Your body releases histamine and other chemicals, resulting in allergic symptoms that accompany inflammation. If the inflammation is on your skin, the most common reactions are a rash or hives. Inflammation in the airways can cause tightening of the throat and lungs, and can lead to severe breathing difficulties that require immediate medical care.

What are the risk factors for food allergies?

A number of factors increase your risk of developing food allergies. Not all people with risk factors will get food allergies. Risk factors for food allergies include:

  • Family history of asthma, hives, or hay fever
  • Personal history of allergies, including asthma and atopy
  • Young age (child)

How are food allergies treated?

There is no effective treatment that can prevent a food allergy except avoiding the offending food, if it is known. Fortunately, following commonsense avoidance practices can decrease the incidence of symptoms of food allergies. Ask what ingredients are in foods before you eat them, and carry appropriate medication in case you inadvertently consume an allergy-causing food. If you have a history of severe food allergies, or anaphylaxis, you should carry an epinephrine kit at all times, and administer epinephrine immediately as needed before seeking emergency care.

Medications such as antihistamines may be used to treat the symptoms of food allergies.

Antihistamines for treatment of food allergy

Antihistamine medications that are effective in the treatment of food allergies include:

  • Cetirizine (Zyrtec)
  • Diphenhydramine (Benadryl Allergy)
  • Loratadine (Alavert, Claritin)

Epinephrine injectors for treatment of food allergy

Epinephrine auto-injectors that are effective in the treatment of severe food allergies include:

  • EpiPen
  • Twinject
  • Care in an emergency setting is effective in the treatment of severe food allergies.

If you have diarrhea and vomiting, fluid and electrolyte replenishment is also a component of successful treatment.

What are the potential complications of food allergies?

You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of food allergies include:

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 18
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Food allergy. National Institute of Allergy and Infectious Diseases. http://www.niaid.nih.gov/topics/foodallergy/understanding/Pages/default.aspx.
  2. Food allergies. FamilyDoctor.org.  http://familydoctor.org/familydoctor/en/diseases-conditions/food-allergies.html
  3. Burks AW, Tang M, Sicherer S, et al. ICON: food allergy. J Allergy Clin Immunol 2012; 129:906.