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.

Eczema and Dermatitis: Diagnosis and Treatment

Eczema:

Acute eczema appears as rash. To differentiate this from psoriasis, this is less well demarcated and less scaly. Eczema can be caused by infection, allergy (atopia), various irritants and venous stasis. Different variety may co exist in a single patient. It is very important to know about the hobby, work or any other source of allergen exposure.

Causes of Eczema:

• Genetic: A family history of allergy (atopy) is common to find in about 70% of patients.

• Infection: Staphylococcus colonized lesions and toxins act as super antigens.

• Allergy: This is very common. Radioallergosorbent test (RAST) help to find out specific causative agent like house dust, mite etc. Food allergy is not also uncommon. Dairy products, eggs can exacerbate eczema. Infants may also suffer from eczema; but fortunately most of them grow out of it by the time they reach teen.

Treatment of eczema:

The patient must understand there is no specific cure available for this condition. Medicines can only control and lessen the symptoms. They tend to have dry skins (Xerosis). This skin gets irritated very easily and becomes itchy. Liberal use of emollients is the mainstay of the treatment. These should be used even when the disease is not active. Conventional soap is better to be avoided. Use emulsifying ointments instead. Emollients to be used at least twice daily. In severe type greasy emollients work best. For less severe variety less greasy products may be used. Topical steroids are also prescribed in a dose depending on the severity, site and patient's age to reduce inflammation and itching.

Dermatitis:

Irritant Dermatitis

We all are susceptible to various kinds of irritants. Most commonly palms are affected. It starts with a dry fissure, which is followed by weeping and itchy lesion.

Common irritants to cause this type of lesions are detergents, soaps, oils, alkalis, repeated use of water, and various solvents. Washing vegetables may also the culprit due the pesticides they contain.

Treatment of irritant dermatitis:

Avoid all the known irritants as far as practicable. Good car of hands by avoiding conventional soaps, liberal emollients, drying the hand properly after washing, using cotton or rubber lined cotton gloves for wet works and use topical steroids intermittently in case of flaring up.

Allergic contact dermatitis

This is often very easy to diagnose as the offending allergen leaves clue by the sharp cut off margins at the lesion. Though there may be secondary spread elsewhere (Auto Sensitization). The common allergens are nickel (watches, jewellery, key and coins); Lanolin (creams and cosmetics), chromates (cements, leather), colophony ( ink, glue, sticking plasters) foam in the furniture, plants (primulas) and medicinal ointments ( antibiotics, antihistamines, anesthetics etc.) This is Type IV type of allergic reaction.

Treatment of contact dermatitis:

Implicated allergen to be removed. To find out the allergen patch testing may be done. Topical steroids are used locally depending on the severity of the condition.

Adult seborrhoeic dermatitis

This is a very common condition. Dandruff being the commonest presentation. It also affect eyebrows, cheeks, and the flexures of the joints. This is caused by the overgrowth of skin yeast in the affected area. This condition can be fulminating in HIV positive patients.

Treatment of seborrhoeic dermatitis:

Use of topical antifungal and steroid ointment intermittently depending on the severity. Dandruff to be treated by Ketoconazole shampoo.

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