People frequently use the term "food allergy" to describe a variety of adverse physical reactions to foods. But a true food allergy is an abnormal response of the body's immune system to certain foods or ingredients.
An abnormal response occurs when the immune system overreacts to substances (usually proteins) that are harmless to most people and starts releasing antibodies called
immunoglobulin E
(IgE). These antibodies attached themselves to special cells called mast cells, which then release substances that cause a variety of allergic reactions.
Symptoms
Food allergies most commonly affect the gastrointestinal tract, the skin and the respiratory system. Typical symptoms include:
- nausea
- vomiting
- diarrhea
- skin rash
- breathing difficulty
- sneezing
- itchy, watery eyes
In severe cases, anaphylactic shock may occur even if the allergic person has consumed only traces of the offending food. The signs of anaphylactic shock include itching and flushing of the skin, followed by severe vomiting, diarrhea,
hypo tension and constricted respiratory passages.
Less sensitive people may be better able to tolerate small amounts of the allergens in the foods they eat. They also may tolerate the allergen if they are not under stress.
Susceptibility
Although two out of five Americans believe that they have food allergies, only about 1 percent of adults suffer from true food allergies. Children are more susceptible -- up to 7 percent may be affected -- but their symptoms often subside as they get older. Some children who as infants had allergies to certain foods are able to eat them again by the age of 3.
The later in life food allergies appear, the less likely they are to go away. Also, people with allergies to plant foods may have cross-allergies. For example, if they are allergic to peanuts, they may also be allergic to other legumes, such as green peas, soybeans, and lentils.
Common Food Allergens
About 90 percent of all food allergies are caused by just a few culprits. The most common allergens include:
- cow's milk
- egg whites
- shellfish and fish
- legumes
- peanuts, walnuts, pecans, almonds and cashews
- wheat
- soybeans
A number of foods commonly believed to be allergenic are not. Chocolate, strawberries, tomatoes, citrus fruits and corn are often blamed for allergic reactions, but they are rarely the cause. Sugar is not an allergenic food, although it is often thought to be.
The majority of adverse reactions to foods are not true food allergies, but rather are sensitivities or intolerances. The symptoms are similar, but these reactions -- unlike allergies -- either don't involve the immune system, or they involve a different part of the immune system than true allergies do.
Diagnosing Food Allergies
Diagnosis usually begins with a physical examination by a physician certified by the American Board of Allergy and Immunology. The qualified allergist will take a detailed medical history.
To help determine which foods affect you adversely, you might be asked to keep a diary of what you eat every day and record any symptoms you experience. You may also be asked to follow an elimination diet, in which all foods that are not very well tolerated are eliminated. These foods are then gradually re-introduced one by one to see if you develop a reaction to them. This process is called a food challenge.
Other diagnostic tools are skin and RAST tests. Whether foods flagged by a skin test actually cause problems can be confirmed by a food challenge.
If the methods described so far do not reveal the source of your symptoms, the gold standard for evaluating allergies is the double-blind challenge test. In this test, the patient takes capsules of dried food suspected of causing reactions, along with capsules containing non-reactive substances; neither the doctor nor the patient knows which is being administered at any given time. If symptoms occur only with the food being tested, the patient is allergic to that food. Double-blind challenges are valuable because they can detect and rule out allergies or intolerances to many foods and other substances such as additives. They also eliminate non-food influences that can cause symptoms, including psychological factors.
Clinical ecologists, cytotoxic testing and sublingual testing are not recommended for reliably determining true food allergies.
How to Cope
Once a food allergy has been diagnosed correctly, the only effective treatment is strict avoidance of the offending food. This can be tricky if you are allergic to something which is used as one of several ingredients in a dish and which cannot easily be detected by sight or smell. (Peanut oil is a good example.) Here are some suggestions that will help keep you from inadvertently ingesting a food to which you are allergic.
In a Restaurant
- Identify your allergy.
- Ask how the dish was prepared.
- Never taste food before asking questions.
At the Supermarket
- Always read the labels on packaged foods.
- Become familiar with unfamiliar names used on labels; for example, sodium caseinate and casein are ingredients to avoid if you are allergic to milk protein.
- If you have questions about favorite foods, contact the manufacturers of the product.
The following chart lists the names for common food allergens.
| MILK |
EGGS |
| Lactalbumin |
Albumin |
| Caseinate |
Vitellin |
| Lacotglobulin |
Ovovitellin |
| Sodium caseinate |
Ovomucin |
| Curds |
Ovomucoid |
| Casein |
Globulin |
| Whey |
Livetin |
| WHEAT |
CORN |
| Gluten |
Corn starch |
| Cracked wheat |
Corn sugar |
| Graham flour |
Corn flour |
| Durum flour
| |
Your allergist may recommend a consultation with a registered dietitian to help you make food choices.
If you are allergic to milk protein, you may find it helpful to choose Kosher foods at the supermarket. Since Orthodox Jews are required to keep milk and meat products separate, a Kosher symbol on a food product is a clear indication of the product's dairy content. Here is a guide to Kosher symbols and what they mean.
- The term parve or pareve after the symbol of the Kosher agency that evaluates the contents means there is no dairy food in the product. For example, the terms K pareve or parve and U pareve or parve signify that no dairy foods are used in the product.
- A "D" after the Kosher agency that evaluates the food means the product contains dairy products. For example, KD or UD means dairy is present.
The symbols usually appear on the front label next to the product name. If a product does not have a "D" or the word pareve or parve next to the Kosher agency symbol, read the ingredients list before assuming that the product does or does not contain dairy.
About Additives
More than 2,000 food additives are commonly used today, including:
- preservatives
- conditioners
- flavorings
- colorants
- sweeteners
The following chart lists food additives that may cause adverse reactions.
| Additive Name
|
Purpose |
| Aspartame |
Sweetener |
| Benzoates |
Preservatives |
| BHA, BHT |
Antioxidants |
| FD and C Dyes |
Colorants |
| MSG |
Flavoring |
| Nitrates/Nitrites
|
Preservatives |
| Parabens |
Preservatives |
| Sulfites |
Preservatives |
Sulfites are among the most widely used additives in prepared foods, and they may also be the most likely culprits when it comes to reaction incidents.
Sulfating agents are used to preserve foods and sanitize containers for fermented beverages. When checking food labels, keep in mind that some sulfites are also known as SO2; these include sulfur dioxide, sodium or potassium sulfite, bisulfite and metabisulfite. Sulfites are commonly found in:
- baked goods
- teas
- condiments
- relishes
- processed seafood products
- jams and jellies
- dried fruit
- fruit juices
- canned vegetables
- dehydrated vegetables
- frozen vegetables
- soup mixes
- beer
- wine
- wine coolers
- hard cider
Until recently, the highest levels of sulfites were in restaurant salad bars. However, because of the growing rate of reaction to sulfites, the Food and Drug Administration banned their use on fruits and vegetables intended to be served raw. The agency also mandated labeling for packaged foods that contain more than 10 parts per million of any sulfiting agent, so that people sensitive to sulfites may easily identify products they should avoid.
