Food allergy has always been a highly topical subject featuring regularly in medical journals. Food intolerance or allergy denotes a reproducible clinical reaction to food. It must be distinguished from food aversions, which comprise psychological avoidance and intolerance, where the clinical response does not occur when the food is given in a disguised form. Not all people who believe they are sensitive to a particular food really are. They may in fact dislike the food, or they may have eaten it coincidentally with the onset of an illness and thereby developed a psychological intolerance.
Food allergies are more common in infants and young children (10-15% of children suffer from symptoms due to food intolerance). Cow’s milk protein intolerance, the most common food allergy in childhood, has a prevalence between 5% and 7.5%. After the age of five years, there is a tendency for the spontaneous disappearance of the food allergy, while allergy to inhaled substances, such as pollens, dust and animal hair, becomes increasingly frequent.
The list of foods that are claimed to cause allergic reactions is very large. It includes such diverse items like eggs, milk, wheat, fish. (especially shellfish and other sea foods), various meats, nuts, mustard, tomatoes, oranges and chocolates!
Allergic reactions may affect any system of the body, producing various symptoms. For example, the skin may show a rash, eczema or swollen patches. The respiratory system may be involved in bronchial asthma, sinusitis or bronchitis. The digestive system may show indigestion, vomiting, abdominal pain, diarrhoea and failure of normal growth.
The other allergic symptoms are headache, swelling of joints, conjunctivitis, swelling of lips and tongue, etc. The claims that allergy may be involved in migraine and epilepsy still require confirmation, though a minority of sufferers from migraine are able to incriminate particular foods, like cheese, chocolate, citrus fruits, and alcoholic drinks as provoking agents. Similarly, hyperactivity in children (usually boys) being aggravated by some artificial food colours is also a subject of controversy.
There are other more specific examples of food sensitivity, the most important of which is coeliac disease or gluten enteropathy. There is malabsorption, weight loss, impaired growth in children, and other manifestations of malnutrition. Coeliac disease is due to atrophy (flattening of the cells) of the inner lining of the small intestine. In this disease, a fraction of wheat, the gluten, acts as the allergen. When wheat is completely eliminated from the diet, patients recover.
One has to be very careful in diagnosing the exact allergen-that is, the food responsible for the causation of allergy symptoms.
In some cases of food allergy, the symptoms develop rapidly and dramatically, almost immediately after eating the offending food, and the diagnosis is easy to make. There are some people, for instance, whose lips swell the moment their mouth touches a peanut, and if by chance they swallow some they will have several systemic symptoms-vomiting, rash, even asthma. More often, it is not so easy to associate symptoms with any particular food, especially if there is a delay of some hours between the eating of the suspected food and the onset of illness. If the symptoms are chronic or recur frequently, they should disappear on a diet (elimination diet) of very few foods (rice, carrots, lettuce, refined oil, sugar, and water) that do not cause food sensitivity. Suspected foods then can be re-introduced one at a time. Skin tests are not very reliable.
It is also observed that people tend to outgrow their allergies. Foods known to have caused reactions in childhood may be tried years later with no reactions at all. All people with a well defined allergy should know about it and inform their doctor. Otherwise they may suffer a severe or even a fatal reaction from a therapeutic injection given for the treatment of some other disease! For instance, a person sensitive to eggs may react badly to immunising injections prepared on an egg medium, such as those for polio or influenza.
Diet
The diet prescription for an allergic person must be specific, individually modified and adjusted, according to the cause of the food allergy.
If the causative food factor is identified, then it can be totally eliminated from the diet, and the sYmptoms would not recur. For example, if the responsible article of food is one that is not consumed regularly (like shellfish), then it can easily be avoided. It is far more difficult in the case of eggs, milk and wheat, which are present in so many foods-cakes, sauces, soups, biscuits, bread, pasta etc.
Substitution of an alternative food may be possible in the case of milk allergy. A person sensitive to cow’s milk may not necessarily be sensitive to goat’s milk. Soybean milk or groundnut milk can also be used as substitutes. Similarly, one sensitive to wheat may do well on oats, rice, barley or corn.
Heating the food may change its properties regarding the causation of allergic symptoms. A person sensitive to raw milk or lightly boiled eggs may be able to tolerate boiled milk or hardboiled eggs. Many times persons sensitive to eggs are able to take the yolks (yellow part) especially if well cooked, although the egg white continues to cause symptoms.
It is not really difficult to live with a food allergy you just have to be a little extra careful!