FOOD ALLERGY

Allergy is one of the health hazards which is generally regarded as any abnormal reaction of a person’s immune system to a foreign substance e.g. pollen grain/ food constituent.

 It is defined as any hypersensitivity reaction towards food with a demonstrated immunological basis.  

1. Types of Allergies

2. Classification of Allergies

3. Allergic foods

4. Allergies reaction

5. Symptoms of Food Allergy

6. Diagnosis

7. Treatment

1. Types of Allergies

Top

An adverse reaction to a food or food component (often a protein) involving reactions of the body’s immune system (immunological reactions). The term “food allergy” should only be used to identify true, immunologically based food allergies-those which affect the body’s immune system. Examples would be allergic reactions to common foods such as cow’s milk, eggs peanuts, and many other. It is preferred over the alternative term, “Food hypersensitivity,” which has been used to describe this type of reaction as well as other types.            

Allergic responses may be organized into four categories noted as Types I-IV.

Type I Allergies

This type of allergies is also known as food anaphylaxis. (The Greek word anaphylaxis means “against protection and refers to allergic reactions to foreign protein molecules). Immediate hypersensitivity – type allergic reactions appear to fall entirely within this category. Type I reactions usually occur within a few minutes to several hours after consumption of the offending food. The observed symptoms of Type I hypersensitivity results from the release of pharmacologically active substances (mediators) such as histamine. This occurs from specific cells in the body known as mast cells, as a consequence of interaction between immunoglobulin E (IgE) and food substances which cause allergic reactions (“allergens”).

Type II and Type III

Allergies: To date, neither Type II nor Type II allergies have been associated with food. However, their differences lie in the time of onset, from four to six hours after exposure.

Type IV Allergies

The Type IV category generally includes the delayed (over hours rather than minutes) hypersensitivity – type allergic responses. This type of allergy is also sometimes called “cellular hypersensitivity,” and generally involves the reaction of certain sensitized cells, usually lymphocytes, to the specific chemical substance that triggers the allergic reaction, the allergen. Type IV allergies may involve food, but in comparison of the reactions is poorly understood at the molecular level. Ultimately, however, the reaction destroys cells. Symptoms appear from 6 to 24 hours after consumption of the offending food.    

2. CLASSIFICATION OF ALLERGIES

Top

1. Immediate allergies
2. Delayed allergies

IMMEDIATE ALLERGIES

1. Are less common in occurrence.
2. Easily recognizable because of immediate symptoms.
3. Clinical features/ symptoms-Nausea, abdominal pain, vomiting. etc.
4. Certain late- phase reactions are eczema, etc..
5. Violent responses and life threatening reaction in some cases.
6. It can be treated with drugs temporarily but is a permanent allergy.

DELAYED ALLERGIES

• Not easily recognizable, takes few hours to days to show symptoms.
• Involves type II, III or IV but do not involve IgE i.e. type I reactions.
• Symptoms are of low grade- headache, indigestion, abdominal pain, fatigue etc., i.e. not fatal
• This is very much prevalent in occurrence.

3. ALLERGIC FOODS

Top

The foods commonly responsible for induction of food allergies include.

LOW ALLERGY FOODS

Apricots, Asparagus, Bananas, Barley, Carrots, Beets, Lettuce, Millet, Oats, Peaches,  Rice, Squash and sweet potato .               

Types of Food Allergic

4. ALLERGIES REACTION AND SYMPTOMS OF FOOD ALLERGY

Top

Allergic Reaction

• Allergic reaction can be provoked by skin contact with poison plants.
• Chemicals and animal scratches, as well as by insect stings. Ingesting or inhaling    substances like pollen.
• Animal dander, molds and mildew, dust, nuts and shellfish, may also cause allergic    reaction.
• Mast cells release histamine when an allergen is encountered.
• The histamine response can produce sneezing, itching, hives and watery eyes

SYMPTOMS

Manifestations of allergy can occur in any part of the body.

• Skin manifestations may includes dermatitis, oedema, fever, blisters, pruritus and urticaria (rashes).
• Common gastrointestinal manifestations, include cheilitis, stomatitis, colic in infants, abdominal distentions, constipation, diarrhoea, dyspepsia and nausea and vomiting.
• Respiratory symptoms include allergic rhinitis, asthma, bronchitis and nasal polyps.
• Neurologic symptoms such as migraine, neuralgias and tension fatigue syndrome (anxiety, fatigue, irritability, muscle and joints ache restlessness, stomach pain).

5. DIAGNOSIS

Top

Dietary History

A careful dietary history should be taken. In certain cases if symptoms develop very rapidly and dramatically after immediate ingesting of the offending food, the patient can make his own diagnosis. In cases of doubt, the patient is given a diary in which he should record all foods eaten and should also record any disturbances occurring due to the food allergy.

Provocative test

In this test, the patients are given a small quantity of the suspected food in a I disguised form so the patient is unaware of the presence of the particular food. Typical symptoms appear at the appropriate time after the meal. The test should be conducted for a minimum of 3 times before obtaining confirmative results. The provocative test should not be conducted in patients who develop severe allergic reactions as it may prove dangerous.

Elimination diet

In this the patient omits one suspected food each day and keeps record of signs and symptoms. This can be adapted in infants and children because of the limited variety of foods they eat, for example, elimination of eggs, milk and wheat which are common allergens in children. These elimination diets are difficult and complicated and normally suited for investigation of patients in hospitals with a dietetic department and physician experienced in study of allergy.

Skin test

The usefulness of the test in diagnosis of food allergy is limited. In intra dermal test minute quantities of extracts containing suspected antigens are packed into the skin over the arm. In scratch test a small amount of the solution containing the antigen is placed into a series of scratches made into the skin. In patch test the antigen is applied to a piece of filter paper over the skin and covered with cellophane and kept for 24 hours. If a red inflammation or hive like wheal appears at the site of contact, the food is suspected to contain the allergen. Sometimes oedema or erythema due to vasodilation is seen.

Radio Allergosorbent test

It is the skin prick test that aim to detect the presence of IgE antibodies. they aim to measure the binding of IgE to allergens such as milk, eggs or fish. An arbitrary score from 0-4 is given. Allergic patients usually have a score above 2. These tests are expensive and not very informative.

X-ray

An X-ray of the GI tract immediately after ingestion of suspected food, admixed with BaS04 will sometimes reveal changes associated with smooth muscle spasm. This only shows the abdominal distress after taking food.

6. TREATMENT

Top

Elimination diets

Elimination diets have a proper place in the diagnosis and management of food intolerance. In elimination diets, the suspected food is excluded in the daily diet.

The common elimination diets are:

i. Simple Exclusion Diets: When a single food like milk, egg, or wheat is suspected, patients are advised how to consume a diet, free of these. This is not simple in practice. Exclusion of food like milk in children, require dietary expertise to ensure that dietary requirements are met.
ii. Multi Exclusion Diet: It is not clear from dietary enquiry or simple exclusion diet which foods are responsible, a complex exclusion diet has to be tried on trial and error basis).
(a) Initial exclusion diets: Initially a wide range of foods which may provoke intolerance is removed from diet and after a period of time, reintroduced singly into the diet so the offending item is identified.
(b) Graduated Exclusion diet: The number of foods excluded from a diet is gradually increased.

Denaturation of protein

Denaturation can help eliminate allergic activity of food, for e.g., patient may be sensitive to raw milk but boiled may be suitable.

Hypersensitisation

Some physicians have been trying to help patients by giving repeatedly small doses of the allergen either by mouth or injection in the hope that their sensitivity may disappear.

Drugs

A number of drugs that mitigate the symptoms of allergy are available. Antihistamines are effective in controlling local forms of allergy like urticaria and angioedema. Although drugs causing somnolence are effective, likely to cause discomfort when taken regularly. Bronchodilator drugs are effective in treatment of bronchial spasms in attacks of asthma. Corticosteroids are highly effective in prevention of attacks. But they can cause adverse effects when used in long term especially in children.

Dietary advice

Patients who are sensitive to eggs may be able to take egg yolk as the egg white is the main allergen. Patient allergic to a particular food should avoid it for atleast a period of time. After some years it can be tried but with great caution, if it is an important article in diet. The patient should be able to recognize the offending food and should inform the doctor before treatment and diagnosis.  

 
Source

Srilakshmi .B 2003.Dietetics, New Age International (P) Publishers Ltd.Chennai.

www.foodallergyhealtheir.com

www.foodallergy.org

www.ifst.org