Do you get a rash when you eat certain foods, smell flowers, or touch dust? Do you keep sneezing? Do your eyes get red and itchy? When things like this happen, we just think, "I have an allergy." So, this blood allergy test is a very important test to find out exactly whether you really have an allergy, and if so, what it is for. Let's talk about this in simple terms today.
What is this blood test for allergies?
Simply put, an allergy blood test measures the amount of antibodies called Immunoglobulin E (IgE) in your blood. Think of our immune system as an army defending a country. When a harmful germ (enemy) enters the body, this army creates special soldiers (antibodies) to fight it.
But, sometimes our immune system makes a small mistake. What happens is that it thinks that even things that are actually harmless to the body, such as dust, pollen, and certain foods, are a big enemy and produces a large amount of these soldiers called (IgE) to fight against them. This unwanted reaction is what we call an allergy . So, a blood test checks whether there are more than normal amounts of these antibodies called (IgE) in your blood.
What are the common things we can be allergic to?
There can be an infinite number of things that cause allergies (allergens). But here are a few things that most people are allergic to:
- Foods: Things like peanuts, milk, eggs, fish, shrimp, crab.
- House dust: Tiny larvae (dust mites) found in dust.
- Latex: Found in things like rubber gloves and socks.
- Insect bites: Insect bites such as bees and wasps.
- Molds: Types of mold that grow in moist places.
- Pets: Fur, saliva, and urine from animals such as dogs and cats.
- Pollen: The stamens of flowers that float in the wind.
- Some medications: For example, medications like penicillin .
Are there types of allergy blood tests?
Yes, there are two main types. It is very important to understand the exact difference between the two.
| Type of test | Simply put... |
|---|---|
| Total IgE Test | This measures the total amount of (IgE) antibodies in your blood. However, this cannot tell you exactly what you are allergic to. Sometimes, even if you have an allergy, the value can be normal. |
| Specific IgE Test | This is the most accurate and widely used method. It measures the amount of IgE antibodies in your blood that are specific to the specific substance you suspect you are allergic to (e.g., peanuts, dust mites). |
When is an allergy blood test needed?
There are several situations in which your doctor may order this test, especially if you have any of the following conditions:
- Allergic rhinitis / hay fever: This is like a cold that won't go away. There is constant sneezing, a runny nose, and a stuffy nose. This is often caused by things in the environment, such as pollen, dust, and animal dander.
- Anaphylaxis: This is a very severe, life-threatening allergic reaction. It can be caused by certain foods (like peanuts) or insect stings. It can cause difficulty breathing, swelling, and even loss of consciousness.
Also, if you frequently experience the following symptoms, this test can help determine if the cause is an allergy.
| Do you also have these symptoms? |
|---|
| - Hives |
| - Itchy, red, or watery eyes |
| - Shortness of breath |
| - Various skin rashes |
| - Frequent sneezing |
| - Itchy or sore throat |
| - Nasal congestion, itching, or runny nose |
| - Swelling of the lips, tongue, eyes, or face |
| - Chest tightness or asthma-like condition (Allergic asthma) |
Is there anything I need to prepare before this blood test?
The simple answer is, ' No. ' You don't need to do or avoid anything special before having this blood test. You don't need to stop eating or drinking or taking any medications. However, only follow any special instructions your doctor gives you.
What does the test report say?
Everyone has some amount of (IgE) in their blood. That's normal. An elevated (IgE) level in the report means you may have an allergy. But there's something important to understand here.
Usually, this blood test cannot tell how severe your allergy is. That is, just because your IgE level is very high does not mean that your reaction will be as severe.
Therefore, after receiving the report, you should definitely talk to your doctor to understand it exactly. If there is a risk of anaphylaxis, a severe allergic reaction, your doctor may also ask you to always carry an epinephrine injection with you in case of an emergency.
Can the results of this test be false-positive?
Yes, it can happen. In fact, studies have found that 50% - 60% of allergy blood test results that show 'positive' or 'allergy' are not actually due to an allergy. This is called a 'False-Positive' result.
This means that even if your blood (IgE) levels are high, you may not actually be allergic to that particular substance (e.g. milk). This is why a doctor doesn't make a decision based on the blood test report alone. He or she will combine your symptoms, the information you provide, and the report to arrive at an accurate diagnosis.
What is the difference between a blood allergy test and a skin allergy test?
These are the two main testing methods used to detect allergies. There are slight differences between the two.
| Feature | Blood Test | Skin Test |
|---|---|---|
| Speed of results | It may take several days. | You can know the results within a few minutes. |
| Accuracy | It may be slightly less expensive than a skin test. | Often gives more accurate results. |
| Who is best suited for? | It is best suited for people with skin conditions, those who cannot stop taking certain allergy medications (antihistamines), and young children. | While suitable for most people, it may not be suitable for those with skin conditions or a history of severe allergies. |
Your doctor will decide which test is most suitable for you.
Take-Home Message
- An allergy blood test measures the level of a special antibody called IgE in your blood. This helps diagnose an allergic condition.
- A positive test result alone does not guarantee that you have an allergy. Your symptoms and medical history are equally important.
- This test usually cannot tell how severe your allergy is.
- Always talk to your doctor about the test results and any further steps you need to take. Avoid making decisions on your own.
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