Blood Tests for Allergies: What You Need to Know
When it comes to diagnosing allergies, there are several testing options available, but one of the most common is the specific IgE (sIgE) blood test. This test helps identify allergic sensitization to various foods, environmental allergens, and even insect venoms. But how reliable is it? When should you opt for a blood test instead of a skin prick test? And what do the results actually mean? Let’s break it down in simple terms.
Skin Prick Test vs. Blood Test – Which One is Better?
For young children, we often prefer the skin prick test because it is painless, fast, and highly accurate. The results are available within 15–20 minutes, and it provides direct insight into whether a person is sensitized to an allergen. However, there are situations where a blood test may be necessary:
✅ If the child or adult cannot stop taking antihistamines (which interfere with skin test results)
✅ If there are severe skin conditions, like uncontrolled eczema that make skin testing difficult
✅ If a blood draw is already being done for other medical reasons, we can simply add the allergy test to avoid an extra procedure
Both tests are valid and play an important role in diagnosing allergies. Here’s how they compare:
What to Expect During an Allergy Blood Test
If you or your child need an allergy blood test, here’s what the process looks like:
🔹 Preparation: No fasting is required. Just make sure to inform your doctor about any medications.
🔹 The Blood Draw: A small amount of blood is taken from a vein, usually from the arm. For all our patients, the smallest butterfly needle is used for your comfort.
🔹 After the Test: There is no downtime—you can go about your day as usual!
Since blood tests take time to be processed, results are usually available within a few days to a week.
For certain selected situations, The Allergy Immunology Clinic can expedite your results to be available within 2 hours.
Understanding Allergy Blood Test Results
One of the most common misconceptions about allergy testing is that a positive test result for foods automatically means an allergy—but this isn’t always true. A blood test measures specific IgE (sIgE) antibodies, which indicate sensitization but not necessarily an actual allergic reaction.
✔️ Some people have positive sIgE results but can eat the food without issues.
✔️ Higher sIgE levels may indicate a higher likelihood of a reaction, but it depends on the individual.
✔️ Your doctor will interpret the results based on your symptoms and medical history.
This is why, for food allergy, an oral food challenge is needed to confirm whether food allergy is truly present.
Not All Allergy Blood Tests Are the Same
There are many laboratories that offer specific IgE (sIgE) blood tests, but not all tests are created equal. The accuracy of the test depends on the lab’s method, equipment, and calibration.
At The Allergy Immunology Clinic, we ensure our patients receive the most accurate and reliable sIgE testing available. We do not use questionable tests like:
❌ IgG testing – Often marketed as a food intolerance test, but it has no scientific basis for diagnosing allergies.
❌ Alcat testing – Claims to detect “food sensitivities” but is not supported by allergy specialists.
If you’re considering allergy testing, make sure you’re using validated, science-backed methods to get accurate answers.
What Happens After the Blood Test?
Once we receive your results, we will:
✔️ Determine whether avoidance is necessary
✔️ Discuss if an oral food challenge is needed to confirm the food allergy
✔️ Assess the possibility of outgrowing the allergy over time
✔️ Provide treatment options, including food immunotherapy and probiotics like Duoflora, which may help with food allergy resolution
We also emphasize the importance of controlling other allergic conditions like eczema, asthma, and allergic rhinitis, as they are all interconnected. Proper management of these conditions can improve allergy outcomes and help speed up food allergy resolution.
Will My Child Outgrow Their Food Allergy?
Over time, many children outgrow allergies to foods like milk or eggs. We monitor this through:
🔹 Regular follow-ups and rechecking sIgE levels or by skin prick test
🔹 Observing if symptoms improve
🔹 Performing an Oral Food Challenge to confirm if the allergy has resolved
If a person passes the Oral Food Challenge, they are encouraged to eat the food regularly to maintain tolerance.
Ready to Get Tested? Schedule a Consultation!
If you suspect allergies for yourself or your child, the best next step is to schedule a consultation with an allergist. At The Allergy Immunology Clinic, we provide expert evaluation, the most accurate allergy testing, and a personalized treatment plan to help you or your child live safely and confidently with your allergies.
📅 Book an appointment today and take the first step toward understanding and managing your allergies!
