We know we're allergic to something, but we don't know exactly what. Or we've suspected a food allergy for years without ever having it confirmed. Allergy tests help to clear up the uncertainty and precisely identify the allergens responsible for the symptoms, which changes the therapeutic approach and daily management.
In Quebec, access to an allergist can be lengthy in the public sector, but first-evaluation options in medical clinics allow the process to begin without delay.
The different types of allergy tests
Skin prick tests are the gold standard for screening IgE-mediated allergies. Small amounts of standardized allergen extracts are applied to the skin, and then the skin is lightly pricked through each extract. A positive reaction, a reddish wheal that appears in 15 to 20 minutes, indicates sensitization to that allergen. These tests are quick, minimally painful, and allow for the simultaneous testing of numerous allergens in a single session.
Specific IgE blood tests, formerly called RAST, measure IgE antibodies directed against specific allergens in a blood sample. They are useful when skin tests cannot be performed, particularly in cases of severe dermatitis, when antihistamines cannot be discontinued, or in young children. Their interpretation requires correlation with the clinical presentation.
For food allergies, oral food challenges can be performed in a controlled medical setting to confirm or refute a suspected allergy, particularly when skin prick tests and blood tests yield ambiguous results.
In Quebec, the following healthcare professionals can prescribe allergy tests: * **Allergists/Immunologists:** These are medical doctors who specialize in diagnosing and treating allergies and immune system disorders. * **General Practitioners (Family Physicians):** Your family doctor can also assess your allergy symptoms and order allergy tests if they suspect an allergy. * **Other Medical Specialists:** Depending on your symptoms, other specialists like dermatologists or pulmonologists might also be involved and can prescribe allergy tests.
Specific IgE blood tests can be prescribed by any physician or nurse practitioner specializing within the scope of a clinical evaluation. Skin tests are generally performed by allergists or physicians trained in allergology. Access to an allergist in Quebec usually requires a medical referral, with varying wait times depending on the region.
For patients without a family doctor, an appointment at a private medical clinic or a telemedicine consultation allows for an initial evaluation, the prescription of appropriate blood tests, and a referral to an allergist if necessary.
What we do with the results
A positive test indicates sensitization to an allergen, meaning the immune system has produced IgE antibodies against that allergen. This does not necessarily mean that this allergen causes real-life symptoms. The correlation between test results and clinical symptoms is essential for correctly interpreting the results.
The results guide several therapeutic decisions: the relevance of targeted allergen immunotherapy, the avoidance measures to implement, the adaptation of drug treatment according to specific allergens, and for food allergies, the definition of a precise eviction diet.
Frequently asked questions about allergy tests
Should I stop my antihistamines before a skin test?
Yes. Antihistamines block the skin reaction and can give false negatives. A discontinuation of five to seven days before the test is usually recommended. The doctor or allergist will specify which medications to stop and the appropriate timeframe.
Are allergy tests covered by the RAMQ?
Blood tests prescribed in a medically justified context are generally covered. Consultation with an allergist is covered by the RAMQ with a medical referral. Tests performed in certain private clinics may incur fees depending on the context.
Are food intolerance tests sold in pharmacies or online reliable?
IgG-based food intolerance tests, often sold directly to consumers, are not scientifically validated for diagnosing allergies or intolerances. They are not recommended by medical allergy societies. An appropriate allergy assessment with a healthcare professional is the reliable approach.
When to consult a healthcare professional
If you suspect a food, respiratory, or skin allergy, if your symptoms are not well controlled despite treatment, or if you wish to consider immunotherapy, a medical consultation is necessary to begin the allergological assessment.
A physician or a nurse practitioner can order the appropriate tests and refer you to an allergist. An in-person or virtual consultation teleconsultation at one of our Omicron Clinic in Quebec gives you quick access.
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