Food allergy

Overview

If you encounter an unpleasant reaction after eating certain foods — hives, itching, swelling or trouble breathing — you may have a food allergy. Then again, you might not.

Many Americans believe they’re allergic to specific foods. But true food allergies aren’t as common as you might think. Less than 2 percent of adults and 8 percent of children actually have a true food allergy. This is little consolation if you’ve had a bad experience and fear a recurrence. That’s why it’s important to distinguish a food allergy from more common problems such as food intolerance, indigestion or other conditions.

Allergy Relief

Some of the medications used to treat respiratory allergy symptoms include antihistamines, decongestants, nasal sprays and eyedrops. What do medications do? Allegra D Allegra Claritin-D Flonase Nasacort Nasacort AQ Nasonex Patanol Zyrtec

If your reaction to a certain food becomes more than an inconvenience or the symptoms are severe, talk with your doctor. Tests can help diagnose food allergies, and you can take precautions to help prevent serious and even life-threatening responses to consuming culprit foods.

Signs and symptoms

Reactions to certain foods are uncomfortable for most people, but for others they are frightening and possibly life-threatening. Symptoms of a food allergy usually develop within an hour of eating the offending food.

The most common signs and symptoms of a true food allergy include:

• Hives, itching or eczema
  
• Swelling of the lips, face, tongue and throat, or other parts of the body
  
• Wheezing, nasal congestion or trouble breathing
  
• Abdominal pain, diarrhea, nausea or vomiting
  
• Dizziness, lightheadedness or fainting

In a severe allergic reaction to food, you may have more extreme versions of the above reactions, or you may experience the following life-threatening signs and symptoms:

• Constriction of airways, including a swollen throat, resulting in trouble breathing
  
• Shock, with a severe drop in blood pressure
  
• Rapid pulse
  
• Dizziness, lightheadedness or loss of consciousness

These signs and symptoms constitute a rare but life-threatening allergic reaction known as anaphylactic shock. About 150 people in the United States die of food-related anaphylaxis each year.

Causes

A true food allergy involves your body’s immune system response to a specific food or component of a food. Your immune system produces immunoglobulin E (IgE) antibodies to fight against even a tiny amount of the culprit food or food component (the allergen). This in turn releases histamine and other chemicals that cause the distressing signs and symptoms that may be a threat to life. Histamine is partly responsible for most allergic responses, including dripping nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, labored breathing and even anaphylactic shock.

The great majority of food allergies are triggered by certain proteins in:

• Cow’s milk
  
• Eggs
  
• Peanuts
  
• Wheat
  
• Soybeans
  
• Fish
  
• Shellfish
  
• Tree nuts

Beans and corn also commonly cause food allergies. Chocolate, long thought by some parents to be a culprit among children, seldom is a cause of allergy.

Other reactions to food don’t involve your immune system or, consequently, the release of histamine. These reactions aren’t true food allergies. Instead, they may be food intolerances. Because food intolerances may involve many of the same signs and symptoms as food allergies do — such as nausea, vomiting, cramping and diarrhea — people often confuse the two.

If you have a food intolerance, you usually can eat small amounts of problem foods without a reaction. By contrast, if you have a true food allergy, even a tiny amount of food may trigger an allergic reaction.

Common causes of food intolerance include:

• Absence of an enzyme needed to fully digest a food. You may not have adequate amounts of some enzymes needed to digest certain foods. Insufficient quantities of the enzyme lactase, for example, make it difficult to digest lactose, the main sugar in milk products. Lactose intolerance can cause bloating, cramping, diarrhea and excess gas.
  
• Irritable bowel syndrome. Certain foods may trigger the symptoms of irritable bowel syndrome. You may find that certain foods will cause cramping, constipation or diarrhea. You may avoid these foods to avoid the symptoms.
  
• Food contaminated by a toxin. Sometimes food poisoning can mimic an allergic reaction. Some types of mushrooms and rhubarb, for example, can be toxic. Bacteria in spoiled tuna and other fish also can make a toxin that triggers adverse reactions.
  
• Recurring stress or psychological factors. Sometimes the mere thought that a food may make you sick actually does. The reason for this is not fully understood.

One of the tricky aspects of diagnosing food intolerance is that some people are sensitive not to the food itself but to a substance or ingredient used in the preparation of the food. This is especially true of foods containing lactose, wheat or sulfites.

Risk factors

Several factors may put you at greater risk of developing a food allergy:

• Genetic disposition. You’re at increased risk of food allergies if other allergies such as hay fever, asthma, hives or eczema are common in your family.
  
• Age. Food allergies are most common in children, especially toddlers and infants. As you grow older, your digestive system matures and your body is less likely to absorb food or food components that trigger allergies. Fortunately, children typically outgrow allergies to milk, soy, wheat and eggs. Severe allergies and allergies to nuts and shellfish are more likely to be lifelong.
  
• Asthma. If you have asthma, you may be sensitive to preservatives containing sulfites. Sulfites are present in wines, fresh and dehydrated fruits, seafoods, maraschino cherries, and some soft drinks. Sulfites are also used to preserve lettuce at some salad bars in the United States and other countries.

When to seek medical advice

See your doctor or allergist if you experience food allergy symptoms shortly after eating. If possible, see your doctor when the allergic reaction is occurring. This will aid in making a diagnosis.

You need emergency treatment immediately if you develop any symptoms of anaphylactic shock.

Screening and diagnosis

The following may help your doctor determine whether you have an actual food allergy:

• A history of your symptoms — which foods, and how much, seem to cause problems — and whether you have a family history of food allergies.
  
• A food diary of your eating habits, symptoms and medication use.
  
• A physical examination to further identify or exclude other medical problems.
  
• Skin prick tests using food extracts to determine your reaction, or a blood test that measures IgE antibody. However, these tests aren’t 100-percent accurate.
  
• Eliminating suspect foods. For a week or two, you may be asked to eliminate suspect foods and add the items back into your diet one at a time. This process can help link symptoms to specific foods. However, this is not a foolproof method. Psychological factors as well as physical factors can come into play. For example, if you think you’re sensitive to a food, a response could be triggered that may not be a true allergic one. If you’ve had a severe reaction to foods, this method cannot be used.

Treatment

For a severe reaction to a food allergy, you may need an emergency injection of adrenaline (epinephrine) and a trip to the emergency room.

If a reaction to certain foods is an annoyance, but not life-threatening, your doctor may prescribe antihistamines to block the symptom-producing release of histamine by your immune system. Creams may relieve skin reactions.

Prevention

The best way to prevent an allergic reaction is to know and avoid foods that cause symptoms. Some people may be merely inconvenienced by this, but others may find it a greater hardship. For instance, if beans are a staple part of your diet, it can be a challenge to come up with a substitute that has equal nutritional value. Also some foods — when used as ingredients in certain dishes — may be well hidden. This is especially true in restaurants and in other social settings.

If you know you have a food allergy, follow these steps:

• Know what you’re eating and drinking. Be sure to read food labels.
  
• If you have already had a severe reaction, wear a medical alert bracelet or necklace.
  
• Talk with your doctor about carrying emergency medications.
  
• If you have asthma, be sure to ask if sulfites have been added to foods when dining in restaurants. When shopping for foods, check labels for the terms sodium bisulfite, potassium bisulfite, sodium sulfite, sulfur dioxide and potassium metabisulfite.

If your child has a food allergy, take these precautions to ensure his or her safety:

• Notify key people that your child has a food allergy. Talk with child care providers, school personnel, parents of your child’s friends, and other adults who regularly interact with your child. Emphasize that an allergic reaction can be life-threatening and requires immediate action. Make sure that your child also knows to ask for help right away if he or she reacts to food.
  
• Explain food allergy symptoms. Teach the adults who spend time with your child how to recognize symptoms of an allergic reaction.
  
• Write an action plan. Your plan should describe how to care for your child when he or she has an allergic reaction to food. Provide a copy of the plan to your child’s school nurse and others who care for and supervise your child.
  
• Have your child wear a medical alert bracelet or necklace. These list your child’s allergy symptoms and explain how others can provide first aid in an emergency.

RELATED STORIES:
Epinephrine: Treatment for anaphylaxis   Allergy treatments   Hives and angioedema   Allergy definitions   Hay fever   Anaphylaxis   Antihistamines: One form of allergy relief   Decongestants: One way to relieve allergy symptoms

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