Post by Lady~RavenHeart on Nov 8, 2005 21:56:14 GMT 2
Food Allergy
Diagnosis of an adverse reaction to a food may be easy if the person consistently exhibits the same symptoms after eating a food. However the diagnosis is most usually more complex as the person is reacting to more than one food, there may be a time delay before the onset of symptoms, and many symptoms can have other causes than an adverse reaction to a food. The same foods can cause different symptoms to different persons, and even with the same person the range of symptoms can change on different occasions. It is therefore important for a patient who believes that they are suffering from an adverse reaction to a food to consult an Allergist or other suitably qualified and experienced specialist doctor who can determine whether the symptoms are indeed related to a food, or is there some other cause.
1. Physical Examination
The diagnosis starts with a complete physical examination followed by laboratory tests to exclude any medical condition not related to adverse reactions to foods.
2. Medical History
It is very important for the doctor to determine the medical history of the patient in order to ascertain the type and severity of the symptoms, to try to rule out any other medical cause of the symptoms, and to try to determine the identity of the problem food(s).
3. Family History
The family history is also important as allergies tend to run in families, so if one or more parents or siblings are allergic, even if with different symptoms to inhalant allergens, then this would increase the chance of the patient also being allergic. Similarly, it is believed that other types of intolerance such as Non-IgE Mediated Immune and Enzymatic Intolerance may also be familial linked.
4. Food History
Information on the personal food pattern is necessary and patients may be required to keep an accurate diary of foods eaten and symptoms experienced over a certain period.
5. Supplementary Tests
After the Medical, Family and Food History have been established, and adverse reaction to food is suspected, then supplementary tests are needed to reach a final and reliable diagnosis. For a patient with a food allergy, as the immune system has been activated and IgE has been produced, then measurement of allergen-specific IgE is used to prove food allergy. Therefore for the diagnosis of food allergy, skin tests and blood tests (Specific IgE) are used to provide further information.
For Food Intolerance, there is no evidence that the immune system is involved, and so the skin and blood tests do not give a positive answer. For the diagnosis of food intolerance, the medical, family and food history, and a selective elimination diet, may give evidence supporting the diagnosis.
5(a) Skin Prick Test
Different types of skin tests can be used to diagnose food allergy. In the skin prick test, a diluted extract or fresh part of the suspected food is placed on the skin of the forearm or the back, which is then scratched or punctured. The skin test is more sensitive and reproducible when fresh food items are used, rather than extracts from commercial manufacturers. The fresh food is punctured with a special needle and then the skin. This is called the "prick-prick method". If, after the prick, a local swelling (wheal) surrounded by redness (flare) forms within 15 minutes, similar to a mosquito bite or larger, then the skin test is positive and the person may be allergic to the tested food. Because food allergen extracts are not standardised, and their stability often remains poorly established, it is important that only experienced doctors interpret results of skin tests. Skin prick testing should be performed only in places equipped to treat anaphylaxis in case of a risk of a systemic reaction. Skin tests are unreliable if a patient has extensive eczema. Another problem can be medication that will interfere with the result of a skin test and that cannot be discontinued for 2 to 14 days because of the severity of the illness, for example antihistamines.
5(b) Blood Test ("ImmunoCAP® Specific IgE")
It is vitally important to distinguish between the blood tests that are used routinely world-wide for the diagnosis of IgE-Mediated Food Allergy, and the unconventional blood tests claiming to identify Food Intolerance.
The blood test used routinely world-wide and in South Africa by thousands of doctors and the medical opinion leaders for the diagnosis of food allergy and the identification of the problem food allergens is the Pharmacia ImmunoCAP® Specific IgE test. This test was originally developed by Pharmacia Diagnostics of Uppsala Sweden in 1972 and has been developed into it's present form. The ImmunoCAP® Specific IgE test is today acknowledged to be the best diagnostic test in the world to measure allergen-specific IgE and is used exclusively throughout all South African pathology laboratories. The ImmunoCAP® Specific IgE test and it's predecessor from Pharmacia have been evaluated over the past 25 years by thousands of independent clinical researchers and their results published in tens of thousands of medical publications throughout the world.
This ImmunoCAP® Specific IgE test measures quantitatively the amount of allergen specific IgE produced by the patients' immune system against any particular food allergen. There is a range of over 200 different food allergens that can be tested for with the ImmunoCAP® Specific IgE test. These ImmunoCAPR Specific IgE food allergen tests include various meats, dairy products, nuts, seeds, beans, cereals, shellfish, fish, molluscs, spices, vegetables, fruits, etc. There are in addition a range of over 200 other allergens that are not of food origin, for example, grass pollens, weed pollens, tree pollens, moulds, epidermals, drugs, occupationals, etc. A positive result with any ImmunoCAP® Specific IgE test clearly and reliably indicates that the patient has IgE directed against that allergen (food) and is therefore sensitised against that food. However, this does not necessarily mean that the patient will exhibit clinical symptoms against that food, especially when the result is only weakly positive. This may mean that the patient is about to develop symptoms. This is why a positive result should be used to identify those allergens to which the patient should then be challenged in an elimination - reintroduction diet. Conversely, a negative ImmunoCAP® Specific IgE result reliably shows that there is no allergen-specific IgE directed against that food, and the patient is therefore not sensitised against that food and the patient is therefore not allergic to that food. This can be very useful information indeed for small babies who appear to be allergic to many foods and it then becomes important to find some foods to which they are not allergic.
In addition to this vast range of individual food allergens with the ImmunoCAP® Specific IgE test, there are various mixes of related foods, such as mixed cereals, mixed seafood, mixed nuts, mixed spices, etc. A particularly useful mixed food allergen test is the Paediatric Food Mix fx5 that tests for allergy to the commonest foods to which a baby or small infant may react, namely egg white, cow's milk, fish, wheat, soya and peanut. These mixed allergen tests are used to screen a blood sample for that type of allergen and a negative result excludes all of those individual components, whereas a positive result would be followed up with tests for the individual component allergens.
ImmunoCAP® Specific IgE test results are expressed in classes from 0 to 6 and fully quantitatively in units of kilo units per litre IgE, (kU/l IgE) and is standardised against the World Health Organisation standard.
In addition to ImmunoCAP® Specific IgE tests to identify food allergens, there are some other blood tests that can be used in the diagnosis of allergy.
The test for Total IgE is a fully quantitative assay that measures the total amount of IgE in the patient, whether it be directed against one or more foods or against inhalant allergens, or drugs or any other allergens. This test is used to give an indication of the degree of allergen load that the patient is being subjected to. For example, a slightly raised Total IgE would indicate that the patient is moderately allergic to just one or a few allergens, whereas a very highly elevated level of Total IgE would indicate that the patient is either highly allergic to one or a few allergens, or is allergic to many allergens. However, due to it's clinical limitations, the test for Total IgE is gradually being replaced by the Phadiatop test and the ImmunoCAP® Specific IgE Paediatric Food Mix fx5.
The Phadiatop® test is a qualitative test (i.e. yes or no) that indicates very reliably if a patient is sensitised to one or more inhalant allergens. Although inhalant allergens are not foods, it must be remembered that many foods are also found as inhalant allergens, for example wheat is a grass that produces pollen that can cause an inhalant allergy. In addition, many infants with food allergy go on to develop inhalant allergy after a few years.
ImmunoCAP® Specific IgE tests have certain advantages over skin prick tests. ImmunoCAP® Specific IgE tests are:
completely unaffected by the symptoms of the patient (e.g. even severe eczema cases)
completely unaffected by drug therapy (e.g. anti-histamines)
are as sensitive as skin tests (i.e. very few false negative results)
are more specific than skin tests (i.e. fewer false positive results)
comprehensive range of allergens that can be tested for (over 200 individual allergens)
screening tests of mixed allergens (over 40 different mixes)
Whether ImmunoCAP® Specific IgE tests or skin prick tests are used depends on the choice of the individual doctor who will base his decision on his own experience and the individual circumstances of each case. Most usually the ImmunoCAP® Specific IgE tests are used due to the advantages stated above, though they are more expensive than skin testing. In South Africa the Total IgE, the Phadiatop and the Specific IgE tests are all fully reimbursed by all Medical Aid Schemes.
5(c) Elimination - Reintroduction Diet
When food allergy to one or more foods is suspected based on the results of the history, supported by skin and/or Specific IgE tests, elimination - reintroduction diets can be used to confirm the diagnosis and the identification of the offending allergens, for two reasons:
the allergens for skin or Specific IgE tests can be affected by loss of allergenicity during manufacture
a substantial number of patients, although demonstrating IgE to that particular food and are therefore sensitised, do not exhibit any clinical symptoms.
An elimination diet is used to remove the suspected foods from the diet for a period of two weeks, even including minute quantities of the suspected allergens. Sometimes the patient is asked to follow an oligoallergic diet that excludes almost all-possible potential allergens. During this period the patient keeps a careful record of the foods consumed and any clinical reactions. If the symptoms do not clearly improve within two weeks then it is most unlikely that food allergy is involved, or there could be multiple sensitivities. If however the symptoms do clearly improve, then it is most likely that the offending food allergens have been correctly identified. An open oral challenge is then performed when the suspected food is re-introduced into the diet or is given under controlled circumstances in the doctors rooms (a challenge test). An adverse reaction then confirms the diagnosis and the identification. If the open challenge is positive the result should ideally be confirmed by a Double Blind Placebo Controlled Food Challenge Test (DBPCFC) where neither the patient nor the doctor are aware of whether the patient is being challenged with the suspected food or with a placebo. As this technique removes any psychological effect and any bias by the doctor, it is regarded as the gold standard for food challenge tests. It is however seldom done in clinical practice due to the inconvenience involved. For the diagnosis of Food Intolerance and the identification of the offending foods, DBPCFC is the only proven test that provides reliable results.
Provocation tests should only be carried out by an experienced doctor with resuscitation equipment readily available, as a severe reaction and even anaphylactic shock is possible.
Diagnosis of Food Intolerance
If the defence (immune) system is not involved, food intolerance cannot be diagnosed by a skin or blood (Specific IgE) test. These IgE tests only detect IgE against a food such as is found with food allergy, and do not give positive results when food intolerance is involved. Therefore food intolerance is diagnosed with the help of the medical history, and food history, followed by elimination and reintroduction or provocation of the suspected food or groups of food. DBPCFC is also of great importance for the diagnosis of food intolerance.
Unconventional Diagnostic Methods
Diagnostic methods used by "clinical ecologists" and others to diagnose and treat patients with the so-called environmental illness (or food and chemical sensitivity / environmentally induced disease / ecologic illness / total allergy syndrome) are expensive and lack scientific foundation in detecting adverse reaction to food, and should be avoided. The theory is that food and chemical sensitivity leads to common somatic complaints such as headache, fatigue, malaise, disorientation and dizziness, among others. This theory has not been proven.
There are in South Africa, and in a very few other countries in the world, some of these tests that are promoted for the diagnosis of food intolerance and the identification of the problem foods. The proponents of these tests claim to identify foods to which a patient is intolerant, and a subsequent exclusion diet will relieve a very wide range of symptoms from migraine to irritable bowel syndrome to chronic fatigue syndrome, and including obesity! These tests are being heavily promoted directly to the public, with largely unsupported medical claims, but against the advice of the vast majority of medical opinion leaders and medical researchers. The most widely publicised of these tests are based on the concept of leukocytotoxic testing, whereby a sample of blood is mixed with the food in question, in a test tube, and the subsequent reaction can be measured by a change in the size of the blood cells. This clinical concept and these tests have over the years been evaluated by local and international opinion leaders in medicine and laboratory pathology and the overall conclusion is that these methods are not recommended for use. They are:
- not supported by mainstream, conventional doctors and researchers
- lacking a scientific rationale,
- not reproducible (i.e. are inconsistent)
- expensive (approximately R2,000 for a standard panel of 130 tests)
These tests are therefore to be regarded as the last line of investigation when all other traditional diagnostic procedures and tests have been used, but to no avail.
Treatment
Once the diagnosis of food adverse reaction has been established and the problem foods reliably identified, then the only proven therapy is to avoid or eliminate the offending food. This means giving up the food that causes the symptoms. In some special situations, the use of prophylactic medications can be beneficial.
If there are several offending foods, or if the foods are a more or less essential part of the diet, such as milk, then a doctor or dietitian with expert knowledge in this area must be consulted. A dietician can be of great help with providing long-term meal planing and can make suggestions for alternative foods or ingredients.
Long term dietary guidelines are only justified after a proper diagnosis has been made. In children, the diagnosis should be considered as temporary and should be re-evaluated at intervals as very young children can "out-grow" many food allergies. For milk and egg allergy, this re-evaluation should be done yearly, while peanut allergy is usually life-long. However, whilst one food allergy can disappear, other food allergies can appear. Also, other types of allergy symptoms can develop and sensitisation to other allergens such as to house dust mites, grass pollens, cats and dogs, etc. (inhalant allergens) can arise.
The Role of the Dietitian
The dietician can play a vital role not only in the treatment (i.e. avoidance) of the offending foods, but even in the diagnosis of the type of food hypersensitivity, and the identification of the problem foods. The dietitian is trained and has many years' experience of food hypersensitivities and their management, whereas the great majority of clinicians, even specialist Allergists, will not have this depth of experience. The value of the dietician in the management of the food allergic patient can therefore not be overstated.
Food Allergy Prevention
There are three main elements to the prevention of food allergy
1. Pre-disposition to Allergy
Children with parents or siblings who suffer from allergies will be more inclined to have allergies themselves. (include graphic here of children and percentages)
2. Breast Feeding
Breast-feeding for a period of 6 months should be encouraged for all new-borns. This becomes clinically important if that child has an allergic pre-disposition, and even after that period known allergenic foods should ideally be avoided if possible. Proteins from potentially allergenic foods such as cow's milk, and egg can be transferred from the mother to the bay in the breast milk, so it is also advisable for the breast-feeding mother to also avoid these potentially allergenic foods. If breast-feeding is not successful or not possible, then a child with an atopic pre-disposition should be given a hypoallergenic formula. Soya milk is not a good alternative as approx. 10% of cow's milk allergic babies are also allergic to soya. (include graphic of breast feeding).
3. Avoidance of Tobacco Smoke and Inhalant Allergens
Passive smoking by a baby or infant is to be strongly discouraged, as this can irritate and sensitise the baby's lungs. Similarly, the exposure to inhalant allergens such as pets and house dust mite, should be avoided as much as possible.
Diagnosis of an adverse reaction to a food may be easy if the person consistently exhibits the same symptoms after eating a food. However the diagnosis is most usually more complex as the person is reacting to more than one food, there may be a time delay before the onset of symptoms, and many symptoms can have other causes than an adverse reaction to a food. The same foods can cause different symptoms to different persons, and even with the same person the range of symptoms can change on different occasions. It is therefore important for a patient who believes that they are suffering from an adverse reaction to a food to consult an Allergist or other suitably qualified and experienced specialist doctor who can determine whether the symptoms are indeed related to a food, or is there some other cause.
1. Physical Examination
The diagnosis starts with a complete physical examination followed by laboratory tests to exclude any medical condition not related to adverse reactions to foods.
2. Medical History
It is very important for the doctor to determine the medical history of the patient in order to ascertain the type and severity of the symptoms, to try to rule out any other medical cause of the symptoms, and to try to determine the identity of the problem food(s).
3. Family History
The family history is also important as allergies tend to run in families, so if one or more parents or siblings are allergic, even if with different symptoms to inhalant allergens, then this would increase the chance of the patient also being allergic. Similarly, it is believed that other types of intolerance such as Non-IgE Mediated Immune and Enzymatic Intolerance may also be familial linked.
4. Food History
Information on the personal food pattern is necessary and patients may be required to keep an accurate diary of foods eaten and symptoms experienced over a certain period.
5. Supplementary Tests
After the Medical, Family and Food History have been established, and adverse reaction to food is suspected, then supplementary tests are needed to reach a final and reliable diagnosis. For a patient with a food allergy, as the immune system has been activated and IgE has been produced, then measurement of allergen-specific IgE is used to prove food allergy. Therefore for the diagnosis of food allergy, skin tests and blood tests (Specific IgE) are used to provide further information.
For Food Intolerance, there is no evidence that the immune system is involved, and so the skin and blood tests do not give a positive answer. For the diagnosis of food intolerance, the medical, family and food history, and a selective elimination diet, may give evidence supporting the diagnosis.
5(a) Skin Prick Test
Different types of skin tests can be used to diagnose food allergy. In the skin prick test, a diluted extract or fresh part of the suspected food is placed on the skin of the forearm or the back, which is then scratched or punctured. The skin test is more sensitive and reproducible when fresh food items are used, rather than extracts from commercial manufacturers. The fresh food is punctured with a special needle and then the skin. This is called the "prick-prick method". If, after the prick, a local swelling (wheal) surrounded by redness (flare) forms within 15 minutes, similar to a mosquito bite or larger, then the skin test is positive and the person may be allergic to the tested food. Because food allergen extracts are not standardised, and their stability often remains poorly established, it is important that only experienced doctors interpret results of skin tests. Skin prick testing should be performed only in places equipped to treat anaphylaxis in case of a risk of a systemic reaction. Skin tests are unreliable if a patient has extensive eczema. Another problem can be medication that will interfere with the result of a skin test and that cannot be discontinued for 2 to 14 days because of the severity of the illness, for example antihistamines.
5(b) Blood Test ("ImmunoCAP® Specific IgE")
It is vitally important to distinguish between the blood tests that are used routinely world-wide for the diagnosis of IgE-Mediated Food Allergy, and the unconventional blood tests claiming to identify Food Intolerance.
The blood test used routinely world-wide and in South Africa by thousands of doctors and the medical opinion leaders for the diagnosis of food allergy and the identification of the problem food allergens is the Pharmacia ImmunoCAP® Specific IgE test. This test was originally developed by Pharmacia Diagnostics of Uppsala Sweden in 1972 and has been developed into it's present form. The ImmunoCAP® Specific IgE test is today acknowledged to be the best diagnostic test in the world to measure allergen-specific IgE and is used exclusively throughout all South African pathology laboratories. The ImmunoCAP® Specific IgE test and it's predecessor from Pharmacia have been evaluated over the past 25 years by thousands of independent clinical researchers and their results published in tens of thousands of medical publications throughout the world.
This ImmunoCAP® Specific IgE test measures quantitatively the amount of allergen specific IgE produced by the patients' immune system against any particular food allergen. There is a range of over 200 different food allergens that can be tested for with the ImmunoCAP® Specific IgE test. These ImmunoCAPR Specific IgE food allergen tests include various meats, dairy products, nuts, seeds, beans, cereals, shellfish, fish, molluscs, spices, vegetables, fruits, etc. There are in addition a range of over 200 other allergens that are not of food origin, for example, grass pollens, weed pollens, tree pollens, moulds, epidermals, drugs, occupationals, etc. A positive result with any ImmunoCAP® Specific IgE test clearly and reliably indicates that the patient has IgE directed against that allergen (food) and is therefore sensitised against that food. However, this does not necessarily mean that the patient will exhibit clinical symptoms against that food, especially when the result is only weakly positive. This may mean that the patient is about to develop symptoms. This is why a positive result should be used to identify those allergens to which the patient should then be challenged in an elimination - reintroduction diet. Conversely, a negative ImmunoCAP® Specific IgE result reliably shows that there is no allergen-specific IgE directed against that food, and the patient is therefore not sensitised against that food and the patient is therefore not allergic to that food. This can be very useful information indeed for small babies who appear to be allergic to many foods and it then becomes important to find some foods to which they are not allergic.
In addition to this vast range of individual food allergens with the ImmunoCAP® Specific IgE test, there are various mixes of related foods, such as mixed cereals, mixed seafood, mixed nuts, mixed spices, etc. A particularly useful mixed food allergen test is the Paediatric Food Mix fx5 that tests for allergy to the commonest foods to which a baby or small infant may react, namely egg white, cow's milk, fish, wheat, soya and peanut. These mixed allergen tests are used to screen a blood sample for that type of allergen and a negative result excludes all of those individual components, whereas a positive result would be followed up with tests for the individual component allergens.
ImmunoCAP® Specific IgE test results are expressed in classes from 0 to 6 and fully quantitatively in units of kilo units per litre IgE, (kU/l IgE) and is standardised against the World Health Organisation standard.
In addition to ImmunoCAP® Specific IgE tests to identify food allergens, there are some other blood tests that can be used in the diagnosis of allergy.
The test for Total IgE is a fully quantitative assay that measures the total amount of IgE in the patient, whether it be directed against one or more foods or against inhalant allergens, or drugs or any other allergens. This test is used to give an indication of the degree of allergen load that the patient is being subjected to. For example, a slightly raised Total IgE would indicate that the patient is moderately allergic to just one or a few allergens, whereas a very highly elevated level of Total IgE would indicate that the patient is either highly allergic to one or a few allergens, or is allergic to many allergens. However, due to it's clinical limitations, the test for Total IgE is gradually being replaced by the Phadiatop test and the ImmunoCAP® Specific IgE Paediatric Food Mix fx5.
The Phadiatop® test is a qualitative test (i.e. yes or no) that indicates very reliably if a patient is sensitised to one or more inhalant allergens. Although inhalant allergens are not foods, it must be remembered that many foods are also found as inhalant allergens, for example wheat is a grass that produces pollen that can cause an inhalant allergy. In addition, many infants with food allergy go on to develop inhalant allergy after a few years.
ImmunoCAP® Specific IgE tests have certain advantages over skin prick tests. ImmunoCAP® Specific IgE tests are:
completely unaffected by the symptoms of the patient (e.g. even severe eczema cases)
completely unaffected by drug therapy (e.g. anti-histamines)
are as sensitive as skin tests (i.e. very few false negative results)
are more specific than skin tests (i.e. fewer false positive results)
comprehensive range of allergens that can be tested for (over 200 individual allergens)
screening tests of mixed allergens (over 40 different mixes)
Whether ImmunoCAP® Specific IgE tests or skin prick tests are used depends on the choice of the individual doctor who will base his decision on his own experience and the individual circumstances of each case. Most usually the ImmunoCAP® Specific IgE tests are used due to the advantages stated above, though they are more expensive than skin testing. In South Africa the Total IgE, the Phadiatop and the Specific IgE tests are all fully reimbursed by all Medical Aid Schemes.
5(c) Elimination - Reintroduction Diet
When food allergy to one or more foods is suspected based on the results of the history, supported by skin and/or Specific IgE tests, elimination - reintroduction diets can be used to confirm the diagnosis and the identification of the offending allergens, for two reasons:
the allergens for skin or Specific IgE tests can be affected by loss of allergenicity during manufacture
a substantial number of patients, although demonstrating IgE to that particular food and are therefore sensitised, do not exhibit any clinical symptoms.
An elimination diet is used to remove the suspected foods from the diet for a period of two weeks, even including minute quantities of the suspected allergens. Sometimes the patient is asked to follow an oligoallergic diet that excludes almost all-possible potential allergens. During this period the patient keeps a careful record of the foods consumed and any clinical reactions. If the symptoms do not clearly improve within two weeks then it is most unlikely that food allergy is involved, or there could be multiple sensitivities. If however the symptoms do clearly improve, then it is most likely that the offending food allergens have been correctly identified. An open oral challenge is then performed when the suspected food is re-introduced into the diet or is given under controlled circumstances in the doctors rooms (a challenge test). An adverse reaction then confirms the diagnosis and the identification. If the open challenge is positive the result should ideally be confirmed by a Double Blind Placebo Controlled Food Challenge Test (DBPCFC) where neither the patient nor the doctor are aware of whether the patient is being challenged with the suspected food or with a placebo. As this technique removes any psychological effect and any bias by the doctor, it is regarded as the gold standard for food challenge tests. It is however seldom done in clinical practice due to the inconvenience involved. For the diagnosis of Food Intolerance and the identification of the offending foods, DBPCFC is the only proven test that provides reliable results.
Provocation tests should only be carried out by an experienced doctor with resuscitation equipment readily available, as a severe reaction and even anaphylactic shock is possible.
Diagnosis of Food Intolerance
If the defence (immune) system is not involved, food intolerance cannot be diagnosed by a skin or blood (Specific IgE) test. These IgE tests only detect IgE against a food such as is found with food allergy, and do not give positive results when food intolerance is involved. Therefore food intolerance is diagnosed with the help of the medical history, and food history, followed by elimination and reintroduction or provocation of the suspected food or groups of food. DBPCFC is also of great importance for the diagnosis of food intolerance.
Unconventional Diagnostic Methods
Diagnostic methods used by "clinical ecologists" and others to diagnose and treat patients with the so-called environmental illness (or food and chemical sensitivity / environmentally induced disease / ecologic illness / total allergy syndrome) are expensive and lack scientific foundation in detecting adverse reaction to food, and should be avoided. The theory is that food and chemical sensitivity leads to common somatic complaints such as headache, fatigue, malaise, disorientation and dizziness, among others. This theory has not been proven.
There are in South Africa, and in a very few other countries in the world, some of these tests that are promoted for the diagnosis of food intolerance and the identification of the problem foods. The proponents of these tests claim to identify foods to which a patient is intolerant, and a subsequent exclusion diet will relieve a very wide range of symptoms from migraine to irritable bowel syndrome to chronic fatigue syndrome, and including obesity! These tests are being heavily promoted directly to the public, with largely unsupported medical claims, but against the advice of the vast majority of medical opinion leaders and medical researchers. The most widely publicised of these tests are based on the concept of leukocytotoxic testing, whereby a sample of blood is mixed with the food in question, in a test tube, and the subsequent reaction can be measured by a change in the size of the blood cells. This clinical concept and these tests have over the years been evaluated by local and international opinion leaders in medicine and laboratory pathology and the overall conclusion is that these methods are not recommended for use. They are:
- not supported by mainstream, conventional doctors and researchers
- lacking a scientific rationale,
- not reproducible (i.e. are inconsistent)
- expensive (approximately R2,000 for a standard panel of 130 tests)
These tests are therefore to be regarded as the last line of investigation when all other traditional diagnostic procedures and tests have been used, but to no avail.
Treatment
Once the diagnosis of food adverse reaction has been established and the problem foods reliably identified, then the only proven therapy is to avoid or eliminate the offending food. This means giving up the food that causes the symptoms. In some special situations, the use of prophylactic medications can be beneficial.
If there are several offending foods, or if the foods are a more or less essential part of the diet, such as milk, then a doctor or dietitian with expert knowledge in this area must be consulted. A dietician can be of great help with providing long-term meal planing and can make suggestions for alternative foods or ingredients.
Long term dietary guidelines are only justified after a proper diagnosis has been made. In children, the diagnosis should be considered as temporary and should be re-evaluated at intervals as very young children can "out-grow" many food allergies. For milk and egg allergy, this re-evaluation should be done yearly, while peanut allergy is usually life-long. However, whilst one food allergy can disappear, other food allergies can appear. Also, other types of allergy symptoms can develop and sensitisation to other allergens such as to house dust mites, grass pollens, cats and dogs, etc. (inhalant allergens) can arise.
The Role of the Dietitian
The dietician can play a vital role not only in the treatment (i.e. avoidance) of the offending foods, but even in the diagnosis of the type of food hypersensitivity, and the identification of the problem foods. The dietitian is trained and has many years' experience of food hypersensitivities and their management, whereas the great majority of clinicians, even specialist Allergists, will not have this depth of experience. The value of the dietician in the management of the food allergic patient can therefore not be overstated.
Food Allergy Prevention
There are three main elements to the prevention of food allergy
1. Pre-disposition to Allergy
Children with parents or siblings who suffer from allergies will be more inclined to have allergies themselves. (include graphic here of children and percentages)
2. Breast Feeding
Breast-feeding for a period of 6 months should be encouraged for all new-borns. This becomes clinically important if that child has an allergic pre-disposition, and even after that period known allergenic foods should ideally be avoided if possible. Proteins from potentially allergenic foods such as cow's milk, and egg can be transferred from the mother to the bay in the breast milk, so it is also advisable for the breast-feeding mother to also avoid these potentially allergenic foods. If breast-feeding is not successful or not possible, then a child with an atopic pre-disposition should be given a hypoallergenic formula. Soya milk is not a good alternative as approx. 10% of cow's milk allergic babies are also allergic to soya. (include graphic of breast feeding).
3. Avoidance of Tobacco Smoke and Inhalant Allergens
Passive smoking by a baby or infant is to be strongly discouraged, as this can irritate and sensitise the baby's lungs. Similarly, the exposure to inhalant allergens such as pets and house dust mite, should be avoided as much as possible.
