Blood Allergy Tests

The Allergy Kit

About Blood Allergy Tests


Blood allergy tests are used when individuals are suspected of suffering from allergies, as physicians will try to determine what allergen is causing allergic reactions in their patients. There are various tests and procedures that can be performed to confirm a diagnosis, including skin prick tests, skin patch tests, blood tests, and the elimination diet when food allergies are suspected.

Skin tests are generally the preferred method for physicians to determine an allergy and they include skin prick tests and skin patch tests. In the skin prick test, a small amount of allergen is injected into the skin and then the area is checked for a reaction. The skin patch test is similar except it is usually performed on the back by placing known allergens on small discs which are taped onto the back for two to three days. Upon removing the discs, if the skin shows a reaction, the allergen has been detected.

Although these are all valid and effective methods, in some cases, the risk of performing a skin test outweighs the benefit and a blood test is the next best method. There are many different types of blood allergy tests that can be used for assessment.

CBC Test

The CBC test is the most basic blood test used in assessing allergies in people. This test simply counts the number of red and white blood cells per cubic millimeter of blood. This test can be used to check for anemia or other blood conditions and is the most basic test to assess general health in individuals.

If a person suffers from asthma, a physician may check for a high level of red blood cells, or polycythemia. When there is an excess amount of red blood cells, it means the individual is not receiving enough oxygen and is producing more red blood cells to try and create enough oxygen in the blood. As a blood allergy test, this test is important because high levels of white blood cells are indicative of inflammatory conditions such as allergies.

Differential White Blood Cell Count

A differential white blood cell count will provide physicians with a percentage of the different types of white blood cells in an individual. For example, if an individual suffers from asthma, a physician will look for a high eosinophil count, indicating a possible allergy. In extreme high levels, a person may be suffering a condition more serious than an allergy, such as a parasitic infection.

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Allergen Specific IgE Antibody Test

Immunoglobulin E, or IgE, is a protein related substance that is usually found in minute amounts in a person’s blood. IgE is actually part of a normal individual’s immune system and it helps to fight foreign substances that threaten one’s health. As you would expect, elevated levels of IgE will alert physicians to the existence of allergies.

This test can be used when a patient has symptoms of allergies to a variety of substances. Negative results to this antibody test probably mean you don’t have an allergy, which involves an IgE response by a patient’s immune system. However, results of this test should be interpreted cautiously because there is a small chance that an allergy may be present even if the test results were negative. If the test does show the presence of elevated IgE antibodies, an allergy is most likely present, but we need to qualify that statement. You may never have an allergic reaction to that particular substance even though you tested positive. Also, the degree of IgE antibody measured does not indicate the severity of a supposed allergy. As you can see, blood allergy tests should be interpreted with caution.

We should note that the conventional method of administering the IgE antibody test has been the RAST test. More recently, most medical laboratories test for specific IgE antibodies using a more modern, immunoassay method. The PRIST test is now the most common immunoassay method used for testing the amount of IgE present in a person’s blood.

Radioallergosorbent Test

In the 1960s, the radioallergosorbent test (RAST) was developed as an in-vitro blood allergy test. This test was created to identify specific IgE antibodies to particular allergens. For each allergen, your body produces a different IgE, so if you’re allergic to milk, your blood has IgE to attack allergenic substances in milk. RASTs are widely available and are unaffected by the presence of medications. Although some studies have proven RASTs to be very effective in diagnosing several of the major food allergies in children, they do seem to miss many allergies as well. If there is a positive RAST result, though, it is usually correct.

RAST results show the concentration of IgE in the blood. Some study outcomes claim that RAST levels can predict whether a child is allergic to egg, milk, peanut, soy, wheat, or fish with a ninety-five percent accuracy rate.

The sed-rate test (also known as ESR or erythrocyte sedimentation rate) is a test for inflammation. When an individual has any inflammation, the amount of proteins in the blood is changed, resulting in blood cells clumping together. This clumping forms residue much faster than what occurs normally. In the case where an individual may be suffering from hives, a sed-rate test can be used to identify any underlying illnesses.

Serum Metabolic Analysis

The serum metabolic analysis is a blood scan that is used to measure electrolytes, such as postassium, and a number of chemical substances that play a role in healthy functioning, such as the liver and kidneys. This test is also helpful in detecting allergens.

To bond proteins with antibodies, blood complement plays a significant role. This action is very important in many immune system functions. In individuals with a blood complement deficiency, outward symptoms may include hives or soft tissue swelling. Complement levels can also determine whether a condition is hereditary or acquired.

Alpha 1-Antitrypsin

Another blood allergy test is one that measures the level of alpha 1-antitrypsin to assess an individual with severe asthma. An alpha1-antitrypsin deficiency can cause emphysema which may be misdiagnosed as asthma. This condition can be hereditary so to ensure that everyone who may be affected is provided appropriate treatment, family members should be tested. In addition, studies have shown that asthma and allergies were significantly higher in groups of patients that were deficient in alpha 1-antitrypsin.

The Allergy Kit


There are several methods to diagnosing an allergy. Physicians will review an individual’s medical history and determine based on the history as well as the severity of reactions, what the best method may be in determining the offending allergens. While skin tests are more commonly performed, in some cases blood allergy tests are a better option to minimize the risk of a severe allergic reaction during the test. Several different types of blood tests can be performed to determine a particular allergy as well as to discover if there are any other underlying health concerns for the individual in question. In cases where patients will not tolerate a blood allergy test, the elimination diet can be used to identify a suspected allergy. During this procedure, several potential allergens are removed from the diet and then gradually introduced back into the diet while an individual is monitored for allergic reactions.

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