Scientific Allergy tests in Food allergy diagnosis.

Allergy tests are not merely remote blood tests. The history usually is the most important diagnostic tool in diagnosing food allergy. The physician interviews the patient to determine if the facts are consistent with a food allergy.  A doctor makes this assessment with the help of a detailed history from the patient,  He or she then confirms the diagnosis by the more objective skin tests, blood tests, or food challenges.If the patient's history, dietary diary,  suggests that a specific food allergy is likely, Double blind placebo food challenge is the gold standard in allergy diagnosis.

A person can have a positive skin test to a food allergen, however, without experiencing allergic reactions to that food. A doctor diagnoses a food allergy only when the patient has a positive skin test to a specific allergen and the history suggests an allergic reaction to the same food. In some highly allergic people, however, especially if they have had anaphylactic reactions, skin tests should not be done because they could provoke another dangerous reaction.  In allergy diagnosis it is the qualified doctor who is the key person to decide  whether to test,what to test , how to test and how to make use of the tests for patients treatment.

Food challenge: The double-blind food challenge has become the gold standard for objective allergy testing. The advantage of a food challenge is  if the patient has an allergic reaction only to the suspected foods and not to the other foods tested, the diagnosis of food allergy is confirmed. This procedure is expensive because it is difficult and requires a lot of time, and can be done only by qualified allergist. if patients symptoms are not due to allergy, additional efforts may be directed at finding the real cause of the patient's symptoms

.Dietary avoidance: Avoiding the offending allergen in the diet is the primary treatment of food allergy. Once a food to which the patient is sensitive has been identified, the food must be removed from the diet. To do this, affected people need to read lengthy, detailed lists of ingredients on the label for each food they consider eating. Many allergy-producing foods such as peanuts, eggs, and milk appear in foods that are not ordinarily associated with them. For example, peanuts often are used as protein supplements, eggs are found in some salad dressings, and milk is in bakery products. The FDA requires that the ingredients in a food be listed on its label. to know about hidden allergens.People can avoid most of the foods to which they are sensitive if they carefully read the labels on foods and, when in restaurants, avoid ordering foods that might contain ingredients to which they are allergic. no medication in any form is available to reliably prevent an allergic reaction to a certain food before eating that food.Food allergy is caused by immune reactions to foods, sometimes in individuals or families predisposed to allergies.

. When a food allergy is suspected, a medical evaluation is the key to proper management.

It is important to distinguish a true food allergy from other abnormal responses to food, that is, food intolerances, which actually are far more common than food It is important to distinguish a true food allergy from other abnormal responses to food, that is, food intolerances, which actually are far more common than food allergy. Once the diagnosis of food allergy is made (primarily by the medical history) and the allergen is identified (usually by skin tests), the treatment basically is to avoid the offending food. People with food allergies should work with their physicians and become knowledgeable about allergies and how they are diagnosed and treated.

KEY POINTS

• Food allergy can be serious. Food allergy can cause symptoms related to any system of body particularly gastrointestinal, skin , eyes and even asthma.
• Food allergy differs from food intolerance, which is far more common.
• The more frequent types of food allergies in adults differ from those in children.
• Children can outgrow their food allergies, but adults usually do not.
• The diagnosis of food allergy is made with a detailed history, the patient's diet diary,mainly by a qualified allergist..
• Food allergy is treated primarily by dietary avoidance.

Food allergy and asthma are both atopic diseases and therefore frequently co-exist.

There is considerable epidemiological evidence to suggest that there is a link between asthma and food allergy.

 Food allergy is common in childhood, affecting approximately 8% of infants.

 Food can induce bronchospasm and food allergy has been implicated as a risk factor for life-threatening asthma.

Additionally, asthma also seems to be a risk factor for life-threatening food allergy.

The role of diet in the aetiology of asthma and as a precipitant of exacerbations has been investigated extensively.

 Many people perceive diet as being an important precipitant of their asthma but objective testing; rather than myths;

 is important to decide any major allergen

The diagnosis is based on a suggestive history supported by skin-prick testing, serum specific IgE or food challenge.

The coexistence of food allergy should be considered in any child with asthma. Where food allergy is confirmed,

 steps should be taken to avoid these foods as this may considerably improve Asthma control and decrease medicine requirements.

It is also pertinent to note that food avoidance  has a timetable and it depends upon which food is an allergen for example milk allergy

may be temporary but wheat avoidance in coeliac disease is lifelong. Food avoidance based upon myths deprives growing children of

 essential nutrients examples being banana and curd loaded with nutrients.

  Food intolerance is not Food allergy . Food intolerance affects nearly everyone at some point.

 When people have an unpleasant reaction to something they ate, they often think that they have an allergy to the food

. People who have food allergies must identify and prevent them because, although usually mild and not severe,

 these reactions can cause devastating illness and, in rare instances, can be fatal.

The allergens in food are those components that are responsible for inciting an allergic reaction.

the symptoms of food allergy occur within a few minutes to an hour of eating.

 A food allergy can initially be experienced as  itching in the mouth and difficulty swallowing and breathing.

Then, during digestion of the food in the stomach and intestines,  , the gastrointestinal symptoms of food allergy like pain

,nausea , vomiting etc occur.

 The allergens are absorbed and enter the bloodstream.and can affect any system of body

Food  allergens can induce rashes, itching, urticaria , eczema ,life threatening angioedema,red eye rapid heart rate , migraine etc,

 when they reach the airways, they can cause asthma.As the allergens travel through the blood vessels, they can cause

lightheadedness,and even anaphylaxis which is a sudden drop in blood pressure. Anaphylactic reactions are severe even when

they start off with mild symptoms, such as a tingling in the mouth and throat or discomfort in the abdomen.

They can be fatal if not treated quickly

 Most allergies to foods begin in the first or second year of life

Exclusive.Breastfeeding for at least the first four months of life appears to help protect high-risk children against milk  allergy and eczema in the first two years of life.. Exclusive breastfeeding should be a consideration, therefore, especially in infants who are predisposed to food allergy. Some children are so sensitive to a certain food, however, that if the mother eats that food, sufficient quantities enter the breast milk to cause a reaction to the food in the child. In this situation, the mothers themselves must avoid eating those foods to which the baby is allergic.  An allergic child who itches, sneezes, and wheezes a lot can feel miserable and, therefore, sometimes misbehave or appear hyperactive. At the other extreme, children who are on allergy medicines that can cause drowsiness may become sleepy in school or at home. Parents and caregivers must understand these different behaviors, protect the children from the foods that induce their allergies and know how to manage an allergic reaction,. Also, schools need to have plans in place to address emergencies,in such children

In Children, the pattern of food allergy is somewhat different from adults, and the most common foods that cause allergic reactions are eggs, milk, peanuts, and fruits, particularly tomatoes and strawberries. Children sometimes outgrow their allergies, but adults usually do not lose theirs. Also, children are more likely to outgrow allergies to cow's milk or soy formula than allergies to peanuts, fish, or shrimp.

Equally important is to understand the concept of cross reactivity..Cross-reactivity is the occurrence of allergic reactions to foods that are chemically or otherwise related to foods known to cause allergy in an individual. If someone has a life-threatening reaction to a certain food, the doctor will counsel that patient to avoid related foods, which also might induce the same reaction. on, and mild swelling of the lips, tongue, palate, and throat. Cross reactivity exists between pollens and foods too. its important to have this knowledge while treating a patient.

 Individuals who are prone to migraines can have their headaches brought on by histamine, which is one of the compounds that mast cells produce in an allergic reaction.In Children, the pattern of food allergy is somewhat different from adults, and the most common foods that cause allergic reactions are eggs, milk, peanuts, and fruits, particularly tomatoes and strawberries. Children sometimes outgrow their allergies, but adults usually do not lose theirs. Also, children are more likely to outgrow allergies to cow's milk or soy formula than allergies to peanuts, fish, or shrimp.

Equally important is to understand the concept of cross reactivity..Cross-reactivity is the occurrence of allergic reactions to foods that are chemically or otherwise related to foods known to cause allergy in an individual. If someone has a life-threatening reaction to a certain food, the doctor will counsel that patient to avoid related foods, which also might induce the same reaction. on, and mild swelling of the lips, tongue, palate, and throat. Cross reactivity exists between pollens and foods too. its important to have this knowledge while treating a patient.

 Individuals who are prone to migraines can have their headaches brought on by histamine, which is one of the compounds that mast cells produce in an allergic reaction.

-- Some natural substances (for example, histamine) in foods can cause reactions resembling allergy. Histamine can reach high levels in cheese, some wines, and certain fish,  from bacterial contamination, especially in food that has not been refrigerated properly.  Histamine toxicity has been referred to as pseudo allergic

  Adverse reaction to Food additives, that are added to food to enhance taste, provide color, are common in modern age. Consumption of these additives can produce symptoms that mimic the entire range of allergic symptoms. The compounds most frequently tied to adverse reactions are yellow dye number 5, MSG, and sulfites. Yellow dye number 5 can cause hives, although rarely. MSG enhances flavor, but when consumed in large amounts, can cause flushing, sensations of warmth, lightheadedness,  facial pressure,chest pain, and feelings of detachment. These symptoms occur soon after eating large amounts of food containing added MSG and are temporary.Allergens survive to cross the gastrointestinal lining, enter the bloodstream, and go to target organs, causing allergic reactions throughout the body. The mechanism of food allergy involves the immune system and heredity.Sulfites occur naturally in some foods and wines and are added to others to enhance crispness or prevent the growth of fungi and keep the salads fresh looking. In high concentrations, sulfites can pose problems for people with severe asthma. The sulfites emit a gas called sulfur dioxide, which the asthmatic inhales while eating the food containing sulfites. This gas irritates the lungs and can induce in an asthmatic a severe constriction of the air passages to the lungs (bronchospasm), making breathing very difficult. Such reactions led the U.S. Food and Drug Administration (FDA) to ban the use of sulfites as spray-on preservatives for fresh fruits and vegetables. Sulfites, however, are still added to some foods, and they also form during the fermentation of wine 

Coeliac disease or wheat allergy in common language is: Intolerance to gluten occurs in a disease called gluten-sensitive enteropathy,. Gluten-sensitive enteropathy is caused by a unique abnormal immune response to certain components of gluten, which is a constituent of the cereal grains wheat, rye, and barley. Although sometimes referred to as an allergy to gluten, this immune response involves a branch of the immune system that is different from the one involved in a classical food allergy. The patients have an abnormality in the lining of the small intestine and experience diarrhea and malabsorption, especially of dietary fat. The treatment for this condition involves the avoidance of dietary gluten.

: Several common   gastrointestinal diseases produce abdominal symptoms that can be  caused by food allergy. The diseases like peptic ulcer, dyspepsia , chronic diarrhea, malabsorption, indigestion etc, must be investigated for food allergies at least in difficult cases.. Eosinophilic gastroenteritis is a definite entity where allergy needs to be tested.