Allergy Blood Test

Introduction:

Blood tests for allergy are done to measure IgE antibodies to a few allergens in the blood. IgE is an antibody made by the body. The most frequently used test for allergy is called RAST (Radioallergosorbent test). An ELISA (Enzyme-Linked Immunosorbent Assay) is a newer blood test form. Blood tests might be done when skin tests cannot be done.

What Are Allergy Blood Tests?

Allergy blood tests check the antibodies called immunoglobulin E (IgE) in the blood. Antibodies are proteins the immune system forms in response to harmful agents like viruses or bacteria. In case of an allergy, the body of every individual produces IgE as soon as the allergen enters, even if it does not cause harm. Common allergens include:

• Some foods or ingredients.

• Dust.

• Latex.

• Insect bites and stings.

• Mold.

• Pet dander.

• Pollens.

• Certain drugs.

This type of allergy test was called a Radioallergosorbent test (RAST) since it used radioactivity but no longer uses radioactivity.

What Are the Different Types of Allergy Blood Tests?

There are two types of allergy blood tests:

Total IgE Test: This test measures the total IgE in the blood.

Specific IgE Test: This test measures the IgE in the blood produced in response to specific allergens.

How Is an Allergy Test Different From a Blood Test?

Both the allergy blood and skin tests are the two most used forms for allergy testing. During an allergy skin test, tiny pinpricks are created in the skin and then applied to an allergen to check for a reaction. Skin test provides immediate results, but blood tests might take a few days. Skin tests are considered more accurate, but some people cannot have allergy skin tests. If a person has any skin condition like hives or rashes or is on an antihistamine drug, allergy skin tests cannot deliver reliable results. In these cases, they may need an allergy blood test.

When Is an Allergy Blood Test Needed?

People might sniffle and sneeze as the season changes or get itchy and teary-eyed when they dust the house or pet an animal. They might start wheezing after eating a particular food.

Allergy blood testing can help identify what triggers the allergy symptoms and help the doctor give an appropriate treatment. An allergy blood test is done in the following circumstances:

• Allergic rhinitis (hay fever) is frequently caused by pollen, pet allergies, or mold (aspergillosis).

• Anaphylaxis is a serious situation and sometimes can become a fatal allergic reaction to a few foods, insect stings, or other allergens.

• Contact dermatitis is caused by contact with irritants such as chemicals, detergents, poisonous plants, or a few metals (like a nickel allergy).

Allergy blood testing is recommended for:

• In case of an unstable heart condition.

• When asthma is poorly controlled.

• In case of severe eczema, psoriasis, or another severe skin condition

The symptoms of allergy are:

• Abdominal pain.

• Cough.

• Diarrhea.

• Dry skin.

• Eczema.

• Headache.

• Hives (urticaria) and swelling (angioedema).

• Itchy, red, or watery eyes.

• Nausea and vomiting.

• Shortness of breath (dyspnea).

• Skin rash.

• Sneezing.

• Sore throat (pharyngitis).

• Stuffy, itchy, or runny nose.

• Swollen lips, tongue, eyes, or face.

• Wheezing, tightness in the chest, or allergic asthma.

How Is an Allergy Blood Test Performed?

Any special preparations are not required for an allergy blood test. In a few cases, the doctor might ask a person to fast (not eat or drink) before the test. If a person is taking antihistamines, they must inform the doctor beforehand. It might be advised to stop taking this medication before the test. An allergy blood test can be conducted within a few minutes. A blood sample is collected in the laboratory. The phlebotomist (a person who draws blood) takes blood from a vein in the arm with the help of a thin needle. The needle may cause a little pinch and discomfort in the area. The collection tube is filled with blood, and the needle is removed. A small bandage is placed on the arm.

Are There Any Risks With an Allergy Blood Test?

An allergy blood test is a simple procedure with no serious risks. Few people might get bruising, light bleeding, or soreness in their arms. These symptoms mostly fade away within a day or two, mostly.

What Do Allergy Blood Test Results Mean?

Some amount of IgE is present in everyone’s blood, but high levels might indicate an allergy. Several labs use various allergy blood test brands, so the scoring system for results can vary from one brand to another. Allergy blood tests do not tell the severity of an allergy. So if a person does have an allergy, they must talk to their doctor about the risk of anaphylaxis. They might need to always carry an emergency epinephrine injection with them.

What Are the Advantages and Disadvantages Associated With Allergy Blood Tests?

The advantages of allergy blood tests are:

• It can be done at any time, regardless of any medications a person takes.

• It requires only one needle pin (unlike skin testing, which requires many). This might be more suitable for people who are scared of needles. Allergy blood testing is the best test for infants and young children.

The disadvantages of allergy blood tests are:

• It is more expensive than skin testing. Many health insurers might not cover it.

• It might be less sensitive as compared to skin tests.

• It might take days or weeks for the results to come as the blood sample is sent to a laboratory for testing. Skin testing gives immediate results.

Conclusion:

An allergy blood test is a test done for testing for a particular substance or an allergen such as a chemical, pollen, food item, etc. It is used for evaluating the amount of IgE in the blood. It is a type of protein found in the blood. It is done if a person has severe heart issues, dermatitis, psoriasis, poorly controlled asthma, allergic rhinitis, etc. This test is preferred over skin testing as it has more reliable results and fewer needles.