What do allergy blood test numbers mean
A food intolerance is not the same as a food allergy. Here’s how to tell the difference.
A food allergy:
- is often to specific foods.
Common food allergies in adults include fish and shellfish and nut allergies. Common food allergies in children include milk, eggs, fish, peanuts and other nuts
- can trigger allergy symptoms, such as a rash, wheezing and itching, after eating just a little quantity of the food (these symptoms generally happen quickly)
- is a reaction by your immune system (your body’s defence against infection). Your immune system mistakenly treats proteins found in food as a threat
- can be life-threatening
A food intolerance:
- only results in symptoms if you eat a substantial quantity of the food (unlike an allergy, where just traces can trigger a reaction)
- causes symptoms that happen gradually, often a few hours after eating the problem food
- does not involve your immune system – there is no allergic reaction, and it is never life-threatening
- can be caused by numerous diverse foods
Find out more about diagnosis of food allergies.
How do I manage it?
If you’re confident you are intolerant to a specific food, the only way to manage this is to stop eating the food for a while and then reintroduce little quantities while monitoring how much you can eat without causing symptoms.
Check food labels to see which sorts of foods to avoid.
If you ponder your kid may own a food intolerance, check with a GP or dietitian before eliminating foods from their diet, as a restricted diet could affect their growth and development. Cows’ milk, for example, is an significant source of calcium, vitamin D and protein.
What causes a food intolerance?
It is often unclear why a person is sensitive to certain foods.
If your symptoms happen after eating dairy products, it’s possible you may have lactose intolerance.
This means your body cannot digest lactose, a natural sugar found in milk, yoghurt and soft cheeses. A GP can generally diagnose lactose intolerance by looking at your symptoms and medical history.
Some people own trouble digesting wheat and experience bloating, wind, diarrhoea, being ill and stomach pain after eating bread.
Read more about wheat intolerance (also known as wheat sensitivity).
Otherwise, the culprit may be a food additive, chemical or contaminant, such as:
- histamine (found in Quorn, mushrooms, pickled and cured foods, and alcoholic drinks)
- artificial sweeteners
- toxins, viruses, bacteria or parasites that own contaminated food
- monosodium glutamate (MSG)
- artificial food colours, preservatives or flavour enhancers
Many people cut gluten from their diet thinking that they are intolerant to it, because they experience symptoms after eating wheat.
But it’s hard to know whether these symptoms are because of an intolerance to gluten, an intolerance to something else in wheat, or nothing to do with wheat at every.
It may assist to read more about cutting out bread from your diet.
Very few people need to cut out gluten from their diet, although it’s significant to do so if you have coeliac disease (which is not an intolerance, nor an allergy, but an autoimmune condition).
What is an allergy blood test?
Allergies are a common and chronic condition that involves the body’s immune system. Normally, your immune system works to fight off viruses, bacteria, and other infectious agents. When you own an allergy, your immune system treats a harmless substance, love dust or pollen, as a threat. To fight this perceived threat, your immune system makes antibodies called immunoglobulin E (IgE).
Substances that cause an allergic reaction are called allergens.
Besides dust and pollen, other common allergens include animal dander, foods, including nuts and shellfish, and certain medicines, such as penicillin. Allergy symptoms can range from sneezing and a stuffy nose to a life-threatening complication called anaphylactic shock. Allergy blood tests measure the quantity of IgE antibodies in the blood. A little quantity of IgE antibodies is normal. A larger quantity of IgE may mean you own an allergy.
Other names: IgE allergy test, Quantitative IgE, Immunoglobulin E, Entire IgE, Specific IgE
Health care providers often need to assess allergic disorders such as allergic rhinoconjunctivitis, asthma, and allergies to foods, drugs, latex, and venom, both in the hospital and in the clinic.
Unfortunately, some symptoms, such as chronic nasal symptoms, can happen in both allergic and nonallergic disorders, and this overlap can confound the diagnosis and therapy.
Studies propose that when clinicians use the history and physical examination alone in evaluating possible allergic disease, the accuracy of their diagnoses rarely exceeds 50%.1
Blood tests are now available that measure immunoglobulin E (IgE) directed against specific antigens.
These in vitro tests can be significant tools in assessing a patient whose history suggests an allergic disease.2 However, neither allergy skin testing nor these blood tests are intended to be used for screening: they may be most useful as confirmatory diagnostic tests in cases in which the pretest clinical impression of allergic disease is high.
In susceptible people, IgE is produced by B cells in response to specific antigens such as foods, pollens, latex, and drugs. This antigen-specific (or allergen-specific) IgE circulates in the serum and binds to high-affinity IgE receptors on immune effector cells such as mast cells located throughout the body.
Upon subsequent exposure to the same allergen, IgE receptors cross-link and initiate downstream signaling events that trigger mast cell degranulation and an immediate allergic response—hence the term immediate (or Gell-Coombs type I) hypersensitivity.3
Common manifestations of type I hypersensitivity reactions include signs and symptoms that can be:
- Cardiovascular (eg, tachycardia, hypotension)
- Gastrointestinal (eg, vomiting, diarrhea)
- Respiratory (eg, acute bronchospasm, rhinoconjunctivitis)
- Cutaneous (eg, acute urticaria, angioedema)
- Generalized (eg, anaphylactic shock).
By definition, anaphylaxis is a life-threatening reaction that occurs on exposure to an allergen and involves acute respiratory distress, cardiovascular failure, or involvement of two or more organ systems.4
The blood tests for allergic disease are immunoassays that measure the level of IgE specific to a specific allergen. The tests can be used to assess sensitivity to various allergens, for example, to common inhalants such as dust mites and pollens and to foods, drugs, venom, and latex.
Types of immunoassays include enzyme-linked immunosorbent assays (ELISAs), fluorescent enzyme immunoassays (FEIAs), and radioallergosorbent assays (RASTs).
At present, most commercial laboratories use one of three autoanalyzer systems to measure specific IgE:
- Immulite (Siemens AG, Berlin, Germany)
- ImmunoCAP (Phadia AB, Uppsala, Sweden)
- HYTEC-288 (Hycor/Agilent, Garden Grove, CA).
These systems use a solid-phase polymer (cellulose or avidin) in which the antigen is embedded. The polymer also facilitates binding of IgE and, therefore, increases the sensitivity of the test.5 Specific IgE from the patient’s serum binds to the allergen embedded in the polymer, and then unbound antibodies are washed off.
Despite the term “RAST,” these systems do not use radiation.
A fluorescent antibody is added that binds to the patient’s IgE, and the quantity of IgE present is calculated from the quantity of fluorescence.6 Results are reported in kilounits of antibody per liter (kU/L) or nanograms per milliliter (ng/mL).5–7
In general, the sensitivity of these tests ranges from 60% to 95% and their specificity from 30% to 95%, with a concordance among diverse immunoassays of 75% to 90%.8
Levels of IgE for a specific allergen are also divided into semiquantitative classes, from class I to class V or VI. In general, class I and class II correlate with a low level of allergen sensitization and, often, with a low likelihood of a clinical reaction.
On the other hand, classes V and VI reflect higher degrees of sensitization and generally correlate with IgE-mediated clinical reactions upon allergen exposure.
The interpretation of a positive (ie, “nonzero”) test result must be individualized on the basis of clinical presentation and risk factors. A specialist can make an significant contribution by helping to interpret any positive test result or a negative test result that does not correlate with the patient’s history.
Allergy blood testing is convenient, since it involves only a standard blood draw.
In theory, allergy blood testing may be safer, since it does not expose the patient to any allergens.
On the other hand, numerous patients experience bruising from venipuncture performed for any reason: 16% in one survey.9 In another survey,10 adverse reactions of any type occurred in 0.49% of patients undergoing venipuncture but only in 0.04% of those undergoing allergy skin testing. Therefore, allergy blood testing may be most appropriate in situations in which a patient’s history suggests that he or she may be at risk of a systemic reaction from a traditional skin test or in cases in which skin testing is not possible (eg, extensive eczema).
Another advantage of allergy blood testing is that it is not affected by drugs such as antihistamines or tricyclic antidepressants that suppress the histamine response, which is a problem with skin testing.
Allergy blood testing may also be useful in patients on long-term glucocorticoid therapy, although the data conflict.
Prolonged oral glucocorticoid use is associated with a decrease in mast cell density and histamine content in the skin,11,12 although in one study a corticosteroid was found not to affect the results of skin-prick testing for allergy.13 Thus, allergy blood testing can be performed in patients who own severe eczema or dermatographism or who cannot safely suspend taking antihistamines or tricyclic antidepressants.
A food intolerance is difficulty digesting certain foods and having an unpleasant physical reaction to them.
It causes symptoms, such as bloating and tummy pain, which generally happen a few hours after eating the food.
The number of people who believe they own a food intolerance has risen dramatically over recent years, but it’s hard to know how numerous people are truly affected.
Numerous people assume they own a food intolerance when the true cause of their symptoms is something else.
What are the symptoms of food intolerance?
In general, people who own a food intolerance tend to experience:
These symptoms generally happen a few hours after eating the food.
It can be hard to know whether you own a food intolerance as these are general symptoms that are typical of numerous other conditions.
Could my symptoms be something else?
If you regularly own diarrhoea, bloating, tummy pain or skin rashes but you’re not certain of the cause, see a GP.
A GP may be capable to diagnose the cause from your symptoms and medical history. If necessary, they’ll order tests, such as blood tests.
You can also do some research yourself. It may help to discover out about other conditions that cause similar symptoms. For example, discover out about:
The bowel is a sensitive organ and it’s common to own bowel symptoms when you own been ill or feel run below or stressed.
Is there a food intolerance test?
A number of companies produce food intolerance tests, but these tests are not based on scientific evidence and are not recommended by the British Dietary Association (BDA).
The best way of diagnosing a food intolerance is to monitor your symptoms and the foods you eat. See what happens when you cut out the suspected food for a while, and then reintroduce it into your diet.
Try keeping a food diary, noting:
- any symptoms you own after eating these foods
- what foods you eat
- when these symptoms happen
Trial elimination diet
Once you own an thought of which foods may be causing your symptoms, you can attempt excluding them from your diet 1 at a time and observing the effect this has.
Try cutting out the suspected food from your diet for 2 to 6 weeks and see if your symptoms improve.
Reintroduce the food to see if symptoms return.
You may discover you can tolerate a certain level and you only get symptoms if you own more than this amount.
Consider seeing a dietitian to make certain you’re receiving every your recommended daily nutrients while you do this trial.
Discover a registered dietitian.
Never restrict your child’s diet unless this has been advised by a dietitian or your doctor.