Food Allergies

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List some common foods one might be allergic to.

What are food allergies?

Do you start itching whenever you eat peanuts? Does seafood cause your stomach to churn? Symptoms like these cause millions of Americans to suspect they have a food allergy.

But true food allergies affect a relatively small percentage of people: Experts estimate that only 2 percent of adults, and from 2 to 8 percent of children, are truly allergic to certain foods. Food allergy is different from food intolerance, and the term is sometimes used in a vague way, making it difficult for people to understand the difference.

Allergy and Intolerance - Different Problems

First let's start by getting the facts straight about food allergies.  The difference between an allergy and an intolerance is how the body handles the offending food. In a true food allergy, the body's immune system recognizes a reaction-provoking substance, or allergen, in the food--usually a protein--as foreign and produces antibodies to halt the "invasion." As the battle rages, symptoms appear throughout the body. The most common sites are the mouth, digestive tract, skin, and the airways. People with allergies must avoid the offending foods altogether.

Cow's milk, eggs, wheat, and soy are the most common sources of food allergies in children. Allergists believe that infant allergies are the result of immunologic immaturity and, to some extent, intestinal immaturity. Children sometimes outgrow the allergies they had as infants, but an early peanut allergy may be lifelong. Adults are usually most affected by tree nuts, fish, shellfish, and peanuts.

Food intolerance is a much more common problem than allergy. Here, the problem is not with the body's immune system, but, rather, with its metabolism. The body cannot adequately digest a portion of the offending food, usually because of some chemical deficiency. For example, persons who have difficulty digesting milk (lactose intolerance) often are deficient in the intestinal enzyme lactase, which is needed to digest milk sugar (lactose). The deficiency can cause cramps and diarrhea if milk is consumed.  It is quite different from the true allergic reaction some have to the proteins in milk. Unlike allergies, intolerances generally intensify with age.

For people with true food allergies, the simple pleasure of eating can turn into an uncomfortable--and sometimes even dangerous--situation. For some, food allergies cause only hives or an upset stomach; for others, one bite of the wrong food can lead to serious illness or even death.

Food intolerance may produce symptoms similar to food allergies, such as abdominal cramping. But while people with true food allergies must avoid offending foods altogether, people with food intolerance can often eat some of the offending food without suffering symptoms. The amount that may be eaten before symptoms appear is usually very small and varies with each individual.

Who is likely to develop a food allergy?

Anyone can develop a food allergy.  However, most allergies occur among people with a family history.  Heredity may cause a predisposition to have allergies of any type, and repeated exposure to allergens starts sensitizing those who are susceptible. Some experts believe that, rarely, a specific allergy can be passed on from parent to child. Several studies have indicated that exclusive breast-feeding, especially with maternal avoidance of major food allergens, may deter some food allergies in infants and young children. (Smoking during pregnancy can also result in the increased possibility that the baby will have allergies.) Most patients who have true food allergies have other types of allergies, such as dust or pollen, and children with both food allergies and asthma are at increased risk for more severe reactions. Children are much more likely to have food allergies than adults, although many allergies are outgrown.

Symptoms?

What are the symptoms of a food allergy?  It is possible that there are different reactions for the same allergen in different people.  Symptoms may appear within seconds or up to several hours after eating the food that triggers the reactions.  In exceptionally sensitive people, just the touch or smell of the food can provoke a reaction!

Common Signs:
The most common symptoms include swelling, sneezing, and nausea.  Most symptoms affect the skin, respiratory system, stomach, or intestines:

     Skin Reactions:
          • Swelling of lips, mouth, tongue, face, or throat
          • Hives
          • Rash or redness
          • Itchy skin or eyes
    
     Nose, Throat, and Lung Reactions:
          • Coughing or wheezing
          • Asthma
          • Breathing difficulty
          • Sneezing
          • Nasal congestion or runny nose

     Stomach and Intestinal Reactions:
          • Vomiting
          • Diarrhea
          • Cramping
          • Gas
          • Nausea
          • Abdominal pain and bloating 

Please be aware that theses symptoms may be caused by other food or nonfood related conditions.  For an accurate diagnosis, a complete medical evaluation will be needed.

Emotions associated with food experiences, and not the food itself, can even cause a reaction.  Just the appearance, smell, or taste of food might trigger an emotional reaction, which results in symptoms that mimic a food allergy or food intolerance.  Or someone might get these symptoms by believing the food is harmful.  Even if you suspect that emotions are at the root of an adverse reaction to food, check with your physician.  Symptoms may stem from a more serious physical condition.

To date, there's no scientific link between food allergies and arthritis, migraine headaches, behavioral problems, ear infections, and urinary tract infections, although research in these areas is underway.

Activity 2:

Can food allergies we dangerous?

Usually reactions to food allergies are more uncomfortable than dangerous.  The greatest danger in food allergy comes from anaphylaxis, a violent allergic reaction involving a number of parts of the body simultaneously. Like less serious allergic reactions, anaphylaxis usually occurs after a person is exposed to an allergen to which he or she was sensitized by previous exposure (that is, it does not usually occur the first time a person eats a particular food). Although any food can trigger anaphylaxis (also known as anaphylactic shock), peanuts, tree nuts, shellfish, milk, eggs, and fish are the most common culprits.

Anaphylaxis can produce severe symptoms in as little as 5 to 15 minutes, although life-threatening reactions may progress over hours. Signs of such a reaction include: difficulty breathing, feeling of impending doom, swelling of the mouth and throat, a drop in blood pressure, and loss of consciousness. The sooner that anaphylaxis is treated, the greater the person's chance of surviving. The person should be taken to a hospital emergency room, even if symptoms seem to subside on their own.

What do you do if you suspect a food allergy?

To diagnose food allergy a doctor must first determine if the patient is having an adverse reaction to specific foods. This assessment is made with the help of a detailed patient history, the patient's diet diary, or an elimination diet.

The first of these techniques is the most valuable. A physician usually sits down with the person suspected of having a food allergy and takes a history to determine if the facts are consistent with a food allergy. The doctor might ask questions such as:

How to Cope with Food Allergies

What should you do if you suspect you have a food allergy?  You'll likely need to avoid the bothersome food - and be cautious when choosing your meals and snacks.  If you must do away with a food, or category of food, plan carefully to ensure that your eating plan is nutritionally adequate and fits your food preference and lifestyle.

Be sure to read food labels for allergens.  Food labels don't include every possible allergen, they will list the top eight, which are 90% of all documented food allergies. They are: milk, eggs, peanuts, tree nuts (such as almonds, cashews and walnuts), fish, shellfish, soy and wheat.

Terms for common allergens

Infants and Children

Milk and soy allergies are particularly common in infants and young children. These allergies sometimes do not involve hives and asthma, but rather lead to colic, and perhaps blood in the stool or poor growth. Infants and children are thought to be particularly susceptible to this allergic syndrome because of the immaturity of their immune and digestive systems. Milk or soy allergies in infants can develop within days to months of birth. Sometimes there is a family history of allergies or feeding problems. The clinical picture is one of a very unhappy colicky child who may not sleep well at night. The doctor diagnoses food allergy partly by changing the child's diet.

If the baby is on a milk based formula with lactose, the doctor may suggest a change to a soy or hypoallergenic formula or exclusive breast milk, if possible. If soy formula causes an allergic reaction, the baby may be placed on a hypoallergenic formula. These formulas are processed proteins (basically sugars and amino acids). There are few if any allergens within these materials. Fortunately, time usually heals this particular gastrointestinal disease and your child will tolerate milk protein. It tends to resolve within the first few years of life.

Exclusive breastfeeding (excluding all other foods) of infants for the first 6 to 12 months of life is often suggested to avoid milk or soy allergies from developing within that time frame. Breast feeding often allows parents to avoid infant-feeding problems, especially if the parents are allergic (and the infant therefore is likely to be allergic). There are some children who are so sensitive to a certain food, however, that if the food is eaten by the mother, sufficient quantities enter the breast milk to cause a food reaction in the child. Mothers sometimes must themselves avoid eating those foods to which the baby is allergic.

There is no conclusive evidence that breastfeeding prevents the development of allergies later in life. It does, however, delay the onset of food allergies by delaying the infant's exposure to those foods that can prompt allergies, and it may avoid altogether those feeding problems seen in infants. By delaying the introduction of solid foods until the infant is 6 months old or older, parents can also prolong the child's allergy-free period.

For more information on allergies, try one of the following sites:

Food Allergy Network - Food Allergy Network website
American Academy of Allergy, Asthma, & Immunology - AAAAI's website

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Revised: 06-13-2008