Few topics in medicine are associated with as much controversy as food allergy. Why? Because diagnosis rests mainly on the history of symptoms-symptoms that may not be accurate and can be mimicked by nonallergic mechanisms as well as allergic mechanisms. Therefore, the Committee on Adverse Reactions to Foods of the American Academy of Allergy and Immunology have agreed on some relevant definitions to help us begin to sort out information concerning allergies:
Adverse Reactions to Foods: This phrase describes any abnormal reaction to a food, whether caused by allergic or nonallergic mechanisms.
Food Allergy or Hypersensitivity Reaction: This phrase describes an abnormal immunologic reaction in which the body’s immune system produces an allergic antibody, called immunoglobulinE (IgE) antibody, to usually harmless foods, such as milk or egg protein, resulting in allergy symptoms, such as wheezing, vomiting or diarrhea. These reactions occur only in some people, usually as a result of a genetic factor, and may be noticeable after the person has eaten just a small amount of the food.
Food Intolerance: This phrase describes a condition far more common than true allergy. This is an abnormal response to food not due to an allergic mechanism. An example of this is milksugar (lactose) intolerance, a condition in which an individual lacks the enzyme to break down the milk sugar for proper digestion. This results in bloating, abdominal discomfort and diarrhea. The precise incidence of food allergy, therefore, is difficult to determine because of difficulty in differentiating allergy from intolerance. However, estimates of cows’ milk allergy range from 0.3 to 7.5 percent. The incidence is higher in infants than adults and may occur in up to 30 percent of all patients with allergic eczema choco lite recenze.
Symptoms Of Food Allergy
Patients with a food allergy can have a variety of symptoms. An example of a severe allergic response is anaphylaxis, a frightening, rapidly occurring reaction. Symptoms can include hives and swelling, swelling of the larynx with hoarseness and a choking sensation, wheezing, severe vomiting and diarrhoea, or even shock. Generally, people experience less severe allergic reactions to foods. The most common reactions are vomiting, diarrhea and skin rashes, including hives and eczema. Respiratory symptoms, including runny nose, sneezing, coughing and wheezing, have also been well documented. Unlike anaphylaxis, these symptoms are not life-threatening and usually occur hours to days after you have ingested the food.
Food allergens are generally derived from the protein component of a particular food. Often these can cause reactions even after they are cooked or have undergone digestion in the intestine. While any food can cause an allergic reaction, the most common culprits are the proteins in cows’ milk, egg white, peanut, nut, wheat, soy and fish (both bony and shell).
Foods are grouped into families according to their origin. For example, peas, beans (including soybean) and peanut are members of the pea or legume family. A1lergy to one member of a food family is often associated with allergy to other members-for example, crossreactivity between soybean and peanut. However, it is not rare to find isolated allergic reactions such as soybean or peanut. Within animal food groups, crossreactivity is not seen as often. That is to say, people allergic to cows’ milk can usually eat beef, and those allergic to egg can usually eat chicken.
Additives and Preservatives
Although not clearly an allergic reaction, adverse reactions to additives and preservatives are important causes of severe, even fatal, reactions. Sulfites are a case in point. They are used as preservatives in some foods and even in some medications. They act primarily as antioxidants, keeping fruits and vegetables looking fresh and crisp longer and preventing the discoloration which makes shrimp less desirable. They can also be found in wine and beer as well as some fruit drinks, dried fruit, baked and processed food. Sulfites are particularly common in restaurants. Sulfites can cause a serious asthma attack in sulfite-sensitive asthmatics, and, in fact, it has been estimated that 5 percent of all asthmatics are likely to be at risk for sulfite sensitivity. Furthermore, sulfites can cause anaphylactic-type shock in these individuals.
The diagnosis of food allergy depends on two criteria. First, there should be a reproducible history of a specific food causing an allergic reaction. Although most allergic reactions occur within two hours after a food is eaten, delayed reactions can occur several hours or even days afterward. Less wellestablished reactions are such phenomenon as headaches (including migraine), stomach aches, fatigue, irritability, hyperactive behavior and other mental disorders. These conditions are often lumped together under the diagnosis of Tension Fatigue syndrome. However, Tension Fatigue syndrome or any of its components have not clearly been shown to be caused by food allergy.
The Food Challenge
The association between the ingestion of a food and symptoms is most often established by an open challenge whereby the person first eliminates the suspected food for one to two weeks and then eats that food. Symptoms are observed over several hours to days to see if there is a cause-and-effect relationship. In some cases a double blind challenge is performed. This is usually done in the doctor’s office, and neither the patient nor the doctor know which food is being challenged. The double blind challenge is thought to be the most objective way of establishing a food allergy. It’s generally done when it’s not clear from the history, skin tests or the open challenge which foods are implicated. Challenges with potentially risky foods must be done under careful medical supervision where an adverse reaction could be treated quickly and aggressively. Finally, in cases where no specific food is suspected by history, a food diary may be useful.
Testing for IgE Antibodies
The second criteria for diagnosing a food allergy involves a demonstration of an allergic antibody (IgE) to that food. The time-honored test is the allergy pinprick skin test. A positive skin test in conjunction with a positive history and challenge cinches the diagnosis. However, a positive skin test alone does not make the diagnosis, nor does a negative skin test necessarily rule out the diagnosis. The RAST (radioallergosorbent test) is a blood test for allergies that provides results similar to those of the skin test. Although it is less sensitive, it can be helpful in the rare cases where skin testing might be risky. Other tests such as cytotoxic blood test and sublingual provocation food testing are not recommended, since these tests are unproven at this time.
The major treatment plan for the person with a proven food allergy is avoidance, since medication and allergy shots have not proven useful. The patient is provided with instructions on which foods to avoid and which foods can be eaten safely. In addition, highly allergic patients must learn to read food labels carefully before eating packaged food, for it is not always obvious that a highly allergenic ingredient is present. It is important to know which particular food causes an allergic reaction, because avoidance is inconvenient and can lead to long-term poor eating habits and malnutrition. In the milk-allergic infant, casein hydrolysates, such as Alimentum or Nutramigen, are usually satisfactory both in terms of their allergenicity and nutritional value. Soy is not generally useful, since 20 to 40 percent of cows’ milk sensitive infants develop soy protein allergy. After infancy the milk allergic patient can use a milk-free creamer for convenience and supplemental calcium. It is critical to adequately supplement the patient who is avoiding major foods to ensure adequate calories, vitamins and minerals intake, particularly in the growing child. Furthermore, since children tend to outgrow food allergies, they should be re-challenged every 6 to 12 months. Finally, patients who have anaphylactic reactions should be taught to inject themselves with adrenalin and have this medication with them at home, school, work and particularly when they go to a restaurant where they may mistakenly ingest an allergy causing food.
The best way to prevent food allergies is to avoid initial sensitization. Recent studies suggest food allergies can be prevented if the problem foods are avoided during the first year of life. Breast-feeding is best, provided the mother limits her intake of cows’ milk, egg and peanut, since these foods can sensitize the infant through the breast milk. Breast-feeding is recommended for at least the first 6 to 12 months. Furthermore, if supplemental milk is required, casein hydrolysates, such as Nutramigen, and the whey hydrolysate, Good Start, have been shown to be useful. Furthermore, if supplemental milk is required, casein hydrolysates, such as Nutramigen, and the whey hydrolysate, Good Start, have been shown to be useful