If you or your doctor suspect an allergy, a blood test can help identify what your immune system is reacting to. Allergen-specific IgE testing is a common, straightforward option that needs only a single blood draw. Here is how it works, how it compares with skin testing, when a blood test is the right choice, and what to know about requisitions and coverage before you get tested in Ottawa.
How allergen-specific IgE blood testing works
When you have an allergy, your immune system makes a type of antibody called immunoglobulin E, or IgE, that is specific to a particular trigger such as peanut, cat dander, or grass pollen. An allergen-specific IgE blood test measures how much of that antibody is present in a sample of your blood for the allergens your provider selects. Higher levels suggest a stronger tendency to react, though results are always interpreted alongside your symptoms and history, not on their own.
Blood test versus skin testing
Skin prick testing, usually done in an allergist's office, places tiny amounts of allergen on the skin and watches for a reaction. It gives fast results and is a well-established approach. IgE blood testing takes a different route: a single blood sample is sent to the lab, and no reaction is provoked on your skin.
- A blood test may be preferred when you have a skin condition like severe eczema that leaves little clear skin to test
- It can be useful when you cannot stop antihistamines, which interfere with skin testing
- It may be chosen when there is any concern about a strong reaction to skin testing
- It is sometimes easier for young children or people who find multiple skin pricks difficult
Neither test is a simple yes-or-no verdict. Your provider combines the results with your story of what happens, and when, to reach a diagnosis.
What a panel can cover
Testing can be ordered for a single suspected allergen or as a panel that groups related triggers together. Your provider chooses what to include based on your symptoms and exposures.
- Foods, such as peanut, tree nuts, milk, egg, shellfish, or wheat
- Environmental triggers, such as dust mites, pet dander, mould, and pollens from trees, grasses, and weeds
- Insect stings and certain other specific allergens where relevant
Requisition and coverage
Allergy blood testing must be ordered by an authorized provider, such as a physician or nurse practitioner, so you will need a requisition; patients cannot self-order it. Coverage varies: some allergy testing is insured under OHIP while some allergen-specific IgE testing is uninsured, meaning payment is required before your sample is collected. Because it depends on the exact tests ordered and your situation, we recommend checking your coverage in advance rather than assuming. If any part of your testing is uninsured, our staff will confirm the cost with you before drawing blood.
Preparing for the test
One advantage of IgE blood testing is that it is easy to prepare for. No fasting is required, so you can eat and drink normally beforehand. Unlike skin testing, you generally do not need to stop antihistamines for a blood test, but always follow the instructions on your requisition and from your provider. The draw itself is a routine blood sample from a vein in your arm.
Where to get allergy testing in Ottawa
Bio-Test Laboratory has served Ottawa-Carleton since 1971 and processes a wide range of specialized bloodwork. Once you have your requisition, most testing is walk-in, first-come, first-served, at any of our 11 locations across the region. Bring your Ontario health card and requisition; no fasting is needed. If any of your allergy testing is uninsured, we will confirm the fee before collection. You can book online through our patient portal, and home visits can be arranged by request for a fee.