|
|
|
 |
Food Allergies
|
|
Unwanted reactions to food can be divided into two basic groups: toxic and nontoxic ones. Toxic reactions can occur in every individual upon consummation of food infested with bacteria and toxins. Nontoxic reaction occur only in hypersensitive individuals and can be allergic (immunologic mechanisms) and non-allergic (food intolerance) which are not caused by immunologic mechanisms. Food allergies can be divided into reactions mediated by IgE antibodies, which is the case with majority of allergic diseases, and those not mediated thereby.
|
|
|
 |
|
How are food allergies manifested?
|
Food allergies mediated by IgE antibodies can be life threatening (anaphylactic shock) or can spread to one or several organic systems. The most frequent ones are skin allergies (urticaria, angioedema, atopic dermatitis). Food allergies are very frequently detected via the so-called oral allergic syndrome, i.e. burning or itching sensation in the tongue, swelling of the tongue, lips, the palate or the pharynx. Asthma and allergic rhinitis signal immediately that the respiratory system has also been affected. Symptoms of the digestive system that refer to food allergy are cramps, nausea, vomiting and diarrhea. Cramps are frequent symptoms of food allergy in nursing infants.
Food allergy not mediated by IgE antibodies can be manifested in special clinic conditions. Diagnosis of such conditions demands careful clinical analysis (allergic eosinophilic gastroenteritis, eterocolitic syndrom, food induced eterophaty, pulmonary hemosiderosis, herpetiform dermatitis, etc.).
|
|
|
|
|
In what age can food allergies develop?
|
|
Such reactions can develop in any age, put most frequently during the first several years. In the developed western countries the frequency of food allergies in children is 8-28%, in adults less frequent, 1.4-1.8%. Food allergies are more frequent in children with some other allergic diseases (atopic dermatitis) or with a family history of that disease
|
|
|
|
|
What type of food most frequently causes allergic reaction?
|
|
Food consists of protein, sugar and fat. The most frequent allergens in food are compounds containing sugar and fat (glycoproteins). Provisions most frequently causing allergies are cow milk, eggs, fish, crabs and clams, cereals, soybeans, peanuts, walnuts, hazelnuts and strawberries. In adults, approx. 90% of food allergies are caused by peanuts, walnuts, fish and clams, whereas in children, by eggs, milk, soybeans and flour. It is a known fact that due to cross-reactivity, patients allergic to pollen can develop food allergy and vice versa. Patients allergic to birch pollen develop frequently allergic reaction to apples, uncooked potatoes, carrots, celery, peas, kiwi, etc.
|
|
|
|
|
Allergy to preservatives, food additives and dyes
|
|
Allergic reactions to food are often caused by food additives, preservatives and dyes. Reactions to additives are manifested in 1% of infants and in 0.01-0.23% of adults. It is believed that reaction to food additives is more frequent, but is not statistically shown due to insufficient and unstandardized testing. Some substances can be identified individually: sodium benzoate preservative, tartrazine dye (yellow dyed beverages, sweets, etc.), and the aspartame sweetener.
|
|
|
|
|
Cow milk allergy
|
|
Cow milk allergy is manifested in approx. 2.5% of nursing infants and of children up two years of age. This is also the most frequent allergy detected in that age. This is attributable to the fact that cow milk proteins are usually the first foreign proteins our body must deal with. Cow milk contains approx. twenty substances that may cause allergic reaction. The most important are globulin, lactalbumin, casein and cow albumin. Pasteurization of the milk decreases its allergenic content. Approx. 50% of patients allergic to cow milk are also allergic to goat milk. Approx. 50% of patients that consume soybean milk due to hypersensitivity to cow milk, can also develop sensitivity to soybean. Fortunately, hypersensitivity to cow milk is very rarely a permanent condition. Approx. 85% of children with detected cow milk allergy cease to be allergic by the time they reach the third year of life and can consume cow milk without any consequences.
|
|
|
|
|
Eggs allergy
|
|
Eggs frequently cause allergic reactions. Egg-white causes allergy more often than yolk. Eggs contain numerous potential glycoproteins that can cause development of allergic hypersensitivity (ovalbumin, ovomucoid, ovotransferrin and lysozyme). Ovalbumin contains more than 50% of the total protein content of the egg-white, both in unboiled and boiled egg. Interestingly enough, patients allergic to eggs have frequently positive skin allergy tests to chicken meat even though they can consume it without allergic reactions.
|
|
|
|
|
Seafood allergy
|
|
Unwanted reactions to fish, clams and crabs can be allergic and non-allergic. Upon consumption of seafood (oily fish, mussels, shrimps) some people experience nausea, vomiting, cramps, urticaria and even anaphylactoid systematic (general) reactions. This is triggered by unspecific (non-allergic) releasing of histamine, the substance present in numerous allergic manifestations. Other, real allergic reactions can occur, especially upon consumption of fish, crabs (crabs and crayfish, lobsters, shrimps), clams (mussels, oysters, limpets), octopuses and squids. Such reactions are more frequent in adults and in persons consuming bigger quantities of seafood. Allergic reactions to fish are usually attributable to trout, salmon, white fish, pike, anchovy, sea bass, tuna, etc. Some fish allergens are thermostable and others lose allergenic features upon heat treatment. Person can be allergic to just one or several types of fish.
|
|
|
|
|
Fruit and vegetable allergies
|
|
Fruit and vegetable allergic reactions are most frequently caused by peanut, hazelnut, walnut, almond, strawberry and kiwi. In young people, allergies are more often triggered by flour (wheat, barley, corn), tomato, parsley, mustard, etc. Some patients can experience the symptoms of allergic rhinitis and asthma upon inhalation of flour, usually during longer occupational exposure (bakers, millers, cooks, etc.) Interestingly enough, such individuals consume food of similar content without any danger of allergic reactions.
|
|
|
|
|
How is food allergy diagnosed?
|
|
Food allergy diagnosis relies very much on the information given by the patient. Patients and in case of children, their parents, often detect connections between allergic symptoms and consumption of a certain kind of food. Patients are instructed to keep a log on their diet and symptoms. Indirect proof of an allergy to a specific type of food is achieved by an elimination diet, i.e. disappearance of allergic reactions upon avoiding consumption of certain type of food. As any other allergy, food allergy can be diagnosed by skin tests and determination of the level of specific IgE antibodies in the patient's blood. The most important test for diagnosing food allergy is provocative (challenge) test. Pursuant to a strict protocol, the patient is given food suspected of causing the allergy in order to monitor appearance of allergic symptoms.
|
|
|
|
|
What to do when food allergy appears?
|
|
Patients allergic to a specific food are recommended to undergo an elimination diet, i.e. to avoid that type of food. It is important to instruct the patient that has experienced systemic (general) allergic reactions (anaphylactic shock) about strict measures for remaining on the elimination diet. It is important to know the types of groceries containing "invisible" allergenic substances (such as eggs in pasta, peanut butter in some industrially manufactures sweets, etc.). Persons exposed to the risk of serious allergic reaction relapses must carry with them a self-administered adrenaline syringe and an instantly active antihistamine.
|
|
|
|
|
Are drugs helpful?
|
|
The most important therapy in patients allergic to food is the elimination diet. If the patient is sensitive to several types of groceries or if the cause of the food allergy has not been diagnosed, it is recommended for the patient to take antihistamine tablets (loratadine, fexofenadine, cetirizine) and a short corticosteroid therapy. Specific immunotherapy is still questionable and is generally not carried out.
|
|
|
|
|
|
 |
|
|
How schools handle food allergy?
A survey of nurses in elementary and middle schools in the U.S. found that food allergy action plans for students with food allergies are used inconsistently.
|
|
|
|
|
|
|
|
|
|
