Blood tests for allergies


You can snort and sneeze when seasons change or have itching and tears when you dust your home or a pet. Maybe you started wheezing when you eat a certain food.

Allergy test (including skin test and blood tests) can determine exactly which allergens are causing your allergy. When you know what they are, you and your doctor can find out the best way to help manage your symptoms.

To find out the allergens that cause your allergy symptoms and help doctors choose the best treatment for you, allergy blood test may bring benefits.

blood tests



  1. What is it?

Blood tests are used to check for allergens known as a specific IgE test but formerly known as RAST test (test radioallergosorbent) method. In the past, these tests are called “RASTs” (an abbreviation of the tests radioallergosorbent) because they use radiation, but tests are not modern. Both blood tests and skin prick tests to detect specific IgE food. IgE binds to cells called mast cells, causes mast cells (a type of cell involved in the immune response of the body) to release chemicals, including histamine, into the bloodstream.  Histamine causes allergic symptoms that many people will be familiar with: rash or hives; sneezing; blocked or runny nose; affect a person’s eyes, nose, throat, lungs, skin, or gastrointestinal tract.

Because IgE antibodies are unique to each allergen (eg, IgE is produced in response to pollen differs from IgE is produced after a bee sting), checking for specific variants can help determine whether an allergy is present. With the skin test, the results are immediate, but blood test results will take at least a few days to arrive. Unlike the skin prick test, blood test is not affected by antihistamines and can be done for people with extensive rash that stop by the skin test.

Different laboratories sometimes use “trademark” of different blood tests and can report results using different scoring system or unit. Common allergens that can be tested using the IgE allergen tests, specifically including:

  • Pollen
  • Musty
  • Animal hair
  • Dust mites
  • The food (including peanuts, milk, eggs, or shellfish)
  • Scaffold
  • Medicines (such as penicillin)
  • Insect venoms (bee or wasp stings)
  • Latex (found in certain balloons or gloves hospital)

Your doctor may also ask a group of tests – sometimes called a mini or mini-panel screen – to detect antibodies against a variety of suspected allergens.

blood tests

  1. The allergy blood tests

Allergy blood test can be called immunoassays, and includes:

  • Total IgE:

This evaluates all IgE in the blood; this is not often a useful test, as some of the conditions that cause high IgE (including eczema) and IgE levels are not necessarily related to food allergy. Allergy blood test is often the screen is at least 10 of the causes of the most common allergies, including dust, pet dander, trees, grass, weeds, and molds related to where you live. They are also particularly useful in the diagnosis of food allergy.

  • Radioallergosorbent test (RAST)

The test looks for antibodies Rast also allergy related specifically to identify your allergens. This measures the amount of IgE to a food allergen specific, (a type of protein can cause a reaction), such as peanuts or eggs. However, the test can give a superior results without the patient has any symptoms (this is known as “sensitive”, it affects a third of the population) and higher IgE is harmless. When a high result be seen in conjunction with allergy symptoms that we can limit the state an “allergy”, and measures should be taken. Therefore, specific IgE testing should only requirements for allergens to which patients have complained about symptoms and random testing is not recommended.

  • Component resolved IgE test:

Also known as component resolved diagnostics (CRD) – this is a very recent development in particular IgE test, under which the laboratory can detect IgE to specific parts of an allergen. Early evidence showing that for some food allergens, such as peanuts, a positive CRD to a specific part of the peanut protein may be more likely to indicate a more serious allergic mild. so some tests are available at the clinic using the CRD method.

  • Table IgE / point of care testing:

Some IgE blood testing kits are now becoming available for patients to use at home or at a pharmacy. Generally, the test is not specific to a particular type of food, and therefore not easy to explain; both false negative and false positive is possible.

There is no special preparation that is necessary before getting an allergy blood test.

  1. How is it done?

Medical history of patients may be asked before getting blood tests and it is especially true if the symptoms recur and appear to be associated with triggers, such as exposure to food or the specific environment, and if the other family members are known to be allergic rotten.

A medical professional will usually draw the blood from a vein. For infants, the blood can be obtained by puncturing the heel with a small needle (lancet). A needle is inserted into a vein (usually in the arm inside of the elbow or the back of the hand) and blood is drawn and collected in vials or syringes. After a few minute, when the process of collecting blood is done, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding

With some tests there is also the potential for serious reactions, including one that can be life-threatening, such as anaphylactic shock. In this case, the IgE antibody test specific allergens can be arranged as an alternative, because it is done on a blood sample and have no influence on the person being tested.

The IgE antibody test specific allergens can also be done to immune surveillance (anesthesia), or to see if a child has grown faster than an allergy.

blood tests

  1. Why allergy blood test is needed?

The aim of blood tests is to find out if you are having a reaction to allergies, and if so, to explore the possible allergens responsible for your symptoms.

Allergy blood test is now considered to be less accurate than the skin prick test, in which a solution of purified allergen is injected or scratched into your skin and response was assessed. This is because blood tests are invasive – it involves taking blood – and more expensive than skin testing. Additionally, while the results of skin allergy tests are available within 20 minutes of the test day, it may take several days to get the blood test results back from the lab.

But there are some people that a blood test may be preferred, or used in conjunction with, check the skin:

  • People who cannot stop taking anti-histamines or certain types of antidepressants for any length of time, and so will not fit a skin prick test (these drugs interfere with the skin prick test)
  • Experiment skin prick is not available;
  • Having skin diseases such as eczema common that might blur the reaction to skin prick test;
  • If skin prick test can cause a severe allergic reaction or did not give clear results.
  • People with skin conditions such as dermatitis, psoriasis, eczema, or, which makes it difficult for them to read the doctor’s skin test results
  • People with dark skin, which can make it difficult for doctors to read skin test results
  • People who are at risk of adverse reaction to a type of allergy test
  • Unable to withstand scratches needle test multiple requests for leather
  • There is an unstable heart condition
  • Has poor asthma control
  • Having severe eczema, dermatitis, psoriasis, or a heavy skincondition
  • There may be an extreme reaction in skin test or a history of life-threatening allergic reaction called anaphylaxis

In rare cases, allergic skin tests relate to dangerous allergic reactions. Blood tests, on the other hand, do not come with a risk of allergic reactions. The main risks include pain or bleeding at the site of needling, or fainting during blood draws.

This test is done to check for allergies to specific allergens. The doctor may ask for it when a child has symptoms of allergy (include hives, itchy eyes or nose, sneezing, nasal congestion, throat tightening, or shortness of breath). The symptoms may be seasonal (eg allergies due to pollens or molds) or year-round (as with pet hair) and can range from mild to severe.

In some cases, the test can also be used to monitor the effectiveness of allergy treatments, or to see if a child has grown faster than an allergy.

Your doctor may also request a blood test to determine yourallergy treatments (immunotherapy) are working well like.

When is it ordered?

One or more antibody tests specific IgE allergen usually ordered when a person has signs or symptoms of suspected anallergy to one or more substances. Signs and symptoms may include:

  • Rash
  • Dermatitis
  • Eczema
  • Itchy red eyes
  • Cough, stuffy nose, sneezing
  • Asthma
  • Itching and tingling in the mouth
  • Abdominal pain or vomiting and diarrhea

A test may also be ordered frequently to help assess the effectiveness of immune therapy or to determine whether a child has grown faster than an allergy.

blood tests

  1. Pros and cons of allergy blood tests

Advantages of the blood allergy tests include:

  • Can be done anytime, regardless medications you are taking
  • Requires only one needle bar (not the same as testing the skin); this may be more attractive for those who are afraid of needles.

The downside of the blood allergy tests include:

  • More expensive than skin testing; many health insurance companies do not include allergy blood test.
  • Can be less sensitive than the skin test
  • Bringing days or weeks to get the results because blood samples must be sent to a laboratory for evaluation. Check the skin providing immediate results.
  1. Allergy blood test results

Blood test results could take several weeks to return, and measuring the amount of IgE antibodies in the blood need to be on a specific level before allergy suspected or confirmed. IgE antibody levels to record not only how severe the allergy is, merely if the patient may be allergic or not. Explaining the results requires care and experience and must always be done by a trained physician in conjunction with clinical history.

Clinical history of a people and a medical allergy test additional monitoring may be needed to confirm the diagnosis of allergies. Similarly, a positive result reveals that a person has a risk of an allergic reaction to the actual physical exposure to that substance. On the other hand, a negative result indicates that a person may not have a “true allergy,” an IgE-mediated reaction to the test specific allergens. The doctor also will review your symptoms and medical history when diagnosing specific allergies.

Your allergies should explain the meaning of your blood tests. The result is not very useful for predicting the severity of the allergy. Instead, the tests provide information about the opportunities that there are allergies. This test is not the same as a pregnancy test, in which a person is or is not pregnant. Normally, the blood test is positive, but who can eat the food without symptoms – they do not have allergies. There are several possible reasons could test as “positive” but that is not true allergies:

Approximately 50-60 percent of all blood tests and skin prick test will bring a “false positive” results. This means that the test shows positive even when you are not actually allergic to the food being tested.

Although the chance is high that the blood test or skin test can be positive even though there are not allergic, or more rarely, negative experiences in the hands of an allergy, blood and skin tests are extremely helpful. This is especially true when the results are understood in the context of your medical history.

blood tests

  1. Side effects of allergy blood tests

Allergy blood tests are relatively safe. However, as with many medical tests, some problems can occur with the taking of the blood, such as:

  • Feeling faint or lightheaded during a blood test
  • Hematoma (accumulation of blood under the skin causing a lump or bruise)
  • The pain, swelling and redness
  • Bleeding at the site where the needle was inserted
  1. What happens after an allergy blood test?

If you have a negative test, it is very unlikely that you have an allergic reaction to allergens such. However, despite a positive test indicates that you are sensitive to allergens (ie, you produce specific IgE antibodies in response to it), it does not show for sure allergens that certainly is the cause of your symptoms. So the doctor will take the signs and symptoms of your account when interpreting a blood allergy test positive.