What are Food allergy and Food intolerance

Many people assign their variety of symptoms to food, and many such victims are seen and started on exclusion diets. The scientific proof that food does damage in most instances is feeble, although unfavorable reactions to food definitely exist. These can be classified into those that involve immune mechanisms as “food allergy” and those that do not involve immune mechanism as “food intolerance”.


Food allergy

Food allergy affect up to about 5% of young children and about 1-2% of adults. This form of allergy may be IgE mediated or non-IgE mediated (T-cell mediated). The IgE mediated reactions occurs within minutes or hour after the ingestion of the food . Adults are more likely to be allergic to fish, shellfish and peanuts, while young children are mostly allergic to cow's milk, egg white, wheat, and soy. Peanuts are very allergenic and when it is there it persists throughout life. The following conditions can result from food allergy


Acute hypersensitivity: After ingestion of nuts, strawberries or shellfish the patient suffers from urticaria , vomiting and diarrhea. These normally don’t pose much problem as the patients are aware and learn to avoid the suspected food. Unintentional eating of the incriminating foodstuff can sometimes occur, leading to angioneurotic oedema, a life threatening condition.

Eczema and asthma: Mostly IgE mediated and affect the children.

Rhinitis and asthma: In the atopic individuals these are mostly produced by milk and chocolates.

Chronic urticaria: Exclusion of particular food releive the problem in most patients

Food-sensitive enteropathy: Coeliac disease (gluten (wheat) sensitive enteropathy), and cow's milk enteropathy (in infants) are the example of this reaction.


Food intolerance

Migraine: Intake of foods like chocolate, cheese and alcohol Some patients suffer from migraine. These foods are rich in certain amines, such as tyramine, which are responsible for such attacks. Those on monoamine oxidase inhibitors, which are involved in the metabolism of these amines, are particularly susceptible.

Irritable bowel syndrome: Though mechanism not clearly understood, certain food precipitates the attack of IBS following ingestion of certain food items, such as wheat.

Chinese restaurant syndrome: dizziness, faintness, nausea, sweating and chest pains may follow after ingestion of Chinese food in some. The responsible agent is Monosodium glutamate, a flavoring agent used in cooking Chinese food.

Lactose intolerance: Abdominal bloating and diarrhea following intake of milk is probably the commonest form of food intolerance all over the world. Lactose present in the milk is the causative factor. This may be genetic in origin

Phenylketonuria: This is also a type of food intolerance, and is due to missing phenylalanine hydroxylase, which is essential for the metabolism of phenylalanine in the protein of the diet

There are other genetic errors of metabolism, which can be regarded as forms of food intolerance.

Food intolerance can occur:

To any constituent of food like the histamine in mackerel or canned food, or the tyramine in cheese.

Or,

Chemical mediators released by food stuff like histamine may be released by tomatoes or strawberries.

Or,

Toxic chemicals present in food like the food additive tartrazine.

Though sometimes thought, there are no evidence to prove that conditions such as arthritis, behavior and affective disorders and Crohn's disease are because of certain type of food ingestion. Multiple vague symptoms such as tiredness or malaise as sometimes blamed are not due to food allergy. Mostly, these patients are victim of some form of psychiatric disorder.


Treatment of food allergies and intolerance:

A careful history may help to outline the contributory mediator, particularly when the effects are instant.

Skin-prick testing with allergen, measurement of antigen or antibodies in the do not correlate with the symptoms and results are usually misleading. 'Fringe' techniques like hair analysis, has negligible value, though advised widely.

Diagnostic exclusion diets are useful but very time-consuming. They can sporadically be of value in recognizing a particular food causing allergy or intolerance.

Dietary challenge is a method where food and the test being given sublingually or by inhalation in an attempt to reproduce the symptoms. Again this may be helpful in small number of cases.

Most people who have acute allergies to food identify it and stop taking the food, and do not usually require medical treatment. In rest of the patients, a small number seem to be helped by modifying their diet, but there is no good scientific substantiation to prove these exclusion diets.