Allergy to different foods is a well recognized phenomenon. Hippocrates, the famouse Greek physician generally regarded as father of medicine in the fifth century B.C., was perhaps, one of the first to record a case of stomach upset and vascular reaction to the skin (urticaria) in a patient who took milk.
Another Greek physician and medical writer Galen in the second century A.D., described a case of allergy to goat’s milk. Numerous reports of allergy to different foods are available.
The ingestion of foods to which the patient is sensitive may produce a variety of symptoms which include itching and swelling of the lips, sores in the mouth, vomiting, gaseous distension, diarrhoea, urticaria, headache. Symptoms around the mouth may appear immediately, while others appear some time later. The same food at some particualr season my produce symptoms, while in others it may not. This depends upon the combination with other allergic factors.
Symptoms of allergy to food taken may appear either soon after, or several hours later; in the later case, it becomes difficult to identify the offending article, of diet.
Food allergy is more common in infants and children. As the child grow older, he is exposed to many more environmental factors. That is why adults are frequently sensitive not only to foods but also to pollens, dusts, moulds, etc., as well.
MILK ALLERGY
Cow’s milk is not an uncommon allergen in infancy, probably because it is the major foreign protein food during the early months of life. It has been estimated that milk allergy occurs approximately in 0.5 per cent of children.
Milk allergy manifests itself by a variety of symptoms. The commonest symptom is that of the infant feeling unwell when he is put on a milk other than that of his mother, and a need is felt to change from one milk to another. Other symptoms pertain to alimentary tract and the respiratory tract. There may also be eczema or urticaria.
Whenever possible the infant should be breast-fed. This reduces the chances of the development of allergic symptoms. Giving of cow’s milk should be delayed up to the age of 9 months to a year in a potentially allergic child.
Many a time, the diagnosis is missed because allergy to milk is not suspected. The best way to make a diagnosis is by eliminating milk from the diet and then rechallenging the process to administer antigen to evoke an immunological response. Milk must be climmated from the diet for at least two weeks. If during this period there is marked improvement in the health of the child, or when reintroduction of milk brings back the symptoms, the diagnosis is established.
After the diagnosis is clinched, the offending milk must be removed from the diet. Milk prepared from soya beans is a good substitute. If it is not locally available, it can be prepared in the house.
The soyabean milk should be given upto a year or so and then a re-trial could be made with the offending milk. If the child does not tolerate it, soya milk may continue to be given; if few symptoms appear then the cow’s milk may gradually be added in the diet.
Soya milk is as nutritious as the mother’s milk; however, this needs to be supplemented with vitamins and minerals.
WHEAT ALLERGY
Next to milk, wheat is the commonest source of food allergy. This is detected when the infant for the first time is given cereal, and develops a rash, abdominal colic or diarrhoea.
An older child or an adult may have asthma or a patch of eczema which is found to be improved by not taking wheat in any form. The treatment is avoidance of wheat in all its different preparations. Duration of avoidance is decided by trying it and seeing wheather it reproduces the symptoms.
EGG ALLERGY
White of an egg is pure albumin (a protein) and being a foreign protein, it is a potent source of allergy. Taking of a raw egg by a person allergic to it, can cause a most severe reaction, including collapse and shock. Even the smell of egg’s contents can cause allergic reactions in highly sensitive people.
SEA FOODS ALLERGY
Fish and other sea foods are amongst the most potent allergic agents. There is cross reaction between various sea foods. Those who have reaction to fish should avoid other sea foods as well. Here again, even the smell of fish can produce urticaria in some people who are strongly allergic to it.
Most of the nuts, e.g., almond, walnut can cause allergic reactions. Persons who are allergic to them, have to avoid them and also preparations like cakes and cookies containing nuts.
Other foods to which people are commOnly allergic are— apples, bananas, cashew nuts, oranges, lemons, grapefruit, mushrooms, watermelons, cucumbers, grapes, gur (not cane-sugar), mustard, radish, onions, garlic, chocolates and soft drinks.
DIAGNOSIS
A thorough history of the patient is of the greatest help in diagnosis. Other procedures that help are elimination diets. Skin tests in food allergy are not of much help.
ELIMINATION DIETS
The patient is instructed to note on a piece of paper all the food he takes and the symptoms, if any, they produce. By studying these daily reports for two to three weeks, one can often detect the onset of symptoms after a new food or after the repeated use of a certain food. The elimination of these foods from the diet one by one, should result in disappearance of symptoms, and the intentional ingestion should be followed by symptoms.
The difficulty arises when the offending food is either milk, egg or wheat, each of which is a common ingredient of many other foods so that its presence is not generally suspected by the patient. It is incumbent on the patient to study and know the ingredients of the food he consumes, so that, he may be better able to avoid any or all of these foods in his diet.