Allergy facts for food

• A food allergy is an immune-mediated side effect of a certain food. For someone with a food allergy, eating or swallowing, even a small portion of a certain food can cause symptoms such as rash, nausea, vomiting, cramps, and diarrhea. Because the body responds to something otherwise harmless, this type of allergic reaction is often referred to as a hypersensitivity reaction. Rarely, a severe allergic reaction can cause a life-threatening set of symptoms called anaphylaxis or anaphylactic shock.
• Although a large proportion of people think they have a food allergy, very few adults and children, mainly under 6 years old, have real food allergies. The rest have what is known as food intolerance, an unwanted response to a food that does not involve the immune system.
• It’s easy to confuse food intolerance with food allergy because they can have similar symptoms. However, with food intolerance, a person usually only has mild symptoms, such as an upset stomach.
  • A well-known example of food intolerance is lactose intolerance, a condition in which a person lacks a certain enzyme needed to digest dairy proteins. The result is loose stools, gas and nausea after consuming dairy products such as milk or cheese.
  • Another example of food intolerance is the response to MSG. MSG, or monosodium glutamate, is a white colored additive used to enhance the taste of food. It is a fermented mixture of glutamic acid, sodium and water and is mainly used in Asian cuisine. In recent decades, MSG’s side effects have been related to its use in Chinese food and have been referred to as Chinese restaurant syndrome. In this syndrome, MSG has been suggested as the cause of the symptoms after a Chinese meal. In 1995, a new term was introduced, the MSG symptom complex, with all reactions reportedly related to MSG. These reactions are not a true food allergy, and the exact cause of the reactions is unknown.

Food Allergy Causes

An allergic reaction occurs when the body’s immune system overreacts to an allergen, in this case a food protein.

• • The white blood cells produce an antibody to this allergen called immunoglobulin E or IgE.
    • When this antibody comes in contact with the specific food protein, it promotes the production and release of certain chemicals called ‘mediators’. Histamine is an example of a mediator.
    • These mediators work on different parts of the body, mainly the skin, throat, airways, intestines and the heart.
    • The effects of the mediators on organs and other cells cause the symptoms of the allergic reaction.
  • Any food has the potential to trigger an allergic reaction, but a few foods are responsible for most food allergies. In fact, most food allergies are triggered by one of these eight foods:
    • Eggs
    • Milk
    • Wheat
    • soy sauce
    • peanuts
    • Tree nuts
    • Fish
    • shellfish
  • Generally, people who are allergic to only a few foods react. Occasionally, a person who is allergic to one food may also be allergic to other related foods. This is called cross reaction. Common examples:
    • Allergy to peanuts – Cross allergies to soybeans, green beans and peas
    • Allergy to wheat – Cross allergy to rye
    • Allergy to cow’s milk: cross allergy to goat’s milk
    • Allergy to pollen – Cross allergies to foods such as hazelnuts, green apples, peaches and almonds
  • People with a history of other allergies, such as eczema or asthma, are particularly prone to food reactions. They are also more likely to have a more serious reaction.

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Food allergy symptoms

A person with a food allergy may develop symptoms from 2 minutes after eating the food, but it may take 1 to 2 hours for the reactions to appear. Occasionally, the symptoms quickly subside and return within 3 to 4 hours.

• • The most common symptoms are the following:
    • Itching of the skin followed by hives, rash of raised, reddish bumps or roots
    • Swelling of the lips and mouth
    • Abdominal cramps
    • Nausea
    • vomit
    • Diarrhea
  • Other symptoms may include the following:
    • Itching and tears in the eyes
    • Runny or stuffy nose
  • Symptoms of a more serious reaction may include the following:
    • Shortness of breath or difficulty breathing
    • Tightness in the chest
    • Sensation of tightness or choking in the throat
    • Rapid or irregular heartbeat
    • Dizzy or light-headed
    • Losing consciousness
  • A serious allergic reaction can be life threatening. This serious reaction is called anaphylaxis or anaphylactic shock.
    • Dizziness, lightheadedness, and loss of consciousness are the result of dangerously low blood pressure called shock.
    • An anaphylactic reaction may start suddenly, or it may develop gradually with itching and swelling of the skin and throat, then progress to a severe reaction in a few hours.
    • Most people get such a reaction immediately after eating the food, but in a few unusual cases, the reaction does not occur until after training after eating the food.
    • Serious reactions are most often seen with allergies to nuts, fish and shellfish, although food allergies can cause anaphylaxis.
    • People with asthma, childhood allergies, eczema, or previous severe food allergies are especially at risk for an anaphylactic reaction.
  • MSG reaction can be mistaken for an allergic reaction.
    • Symptoms of MSG reaction include:
      • Burning sensation at the back of the neck and radiant along the arms and chest
      • Tingling and numbness in the same areas
      • Headache
      • Nausea
      • Occasionally, breathing difficulties, especially in people with poorly controlled asthma
    • A few people experience seizures, irregular heartbeat and anaphylaxis after using MSG.
    • Contrary to popular belief, MSG has no relationship to Alzheimer’s disease, Huntington’s chorea, or other chronic diseases.

When should you seek medical care for food allergy?

If someone is experiencing food allergy symptoms, contact a healthcare provider immediately for advice.

• • He or she may recommend that you go to a hospital’s emergency department.
  • If the person is unable to reach a health care provider and is concerned about their symptoms, they should go to the emergency department.
  • Serious reactions, including symptoms such as difficulty breathing, dizziness or lightheadedness, or tightness or suffocation in the throat, should be treated in an emergency department.
  • Even mild symptoms that don’t improve or worsen should be evaluated in an emergency department.

The person should not attempt to drive to the hospital. If no one is available to drive the person immediately, call 9-1-1 for emergency medical transportation. While you wait for the ambulance to arrive, wait for self-treatment.

Food allergy diagnosis

In general, a food allergy is identified by signs and symptoms. Medical professionals are trained to recognize hives, swelling patterns, rashes and other symptoms associated with allergic reactions.

The person will be asked about their medical history and possible triggers of the reaction.

Blood tests and other tests are only needed under very unusual circumstances, such as anaphylaxis.

Some people can determine which foods caused the allergic reaction, especially if the reaction occurs within minutes of consuming a particular food. Many others will need to see an allergist for special tests to determine the correct food that is responsible.