Congratulations on scheduling your allergy test! You’re taking an excellent step towards effective management. Before your test, your allergist will give you a couple of guidelines to ensure the most accurate test possible. One such guideline pertains to your allergy medications, specifically: antihistamines.
Let’s look at how allergy testing works and when you should stop taking antihistamines before your test.
How Allergy Testing Works
There are two standard types of allergy tests:
- Skin tests. A skin scratch or prick test is the most common type of allergy testing. During the test, your allergist will place a small drop of an allergen on the skin and then lightly scratch the area to introduce the substance into your system or lightly puncture the skin with the allergen. Reactions typically occur within the first 15 minutes of the test and will appear as a red rash.
- Blood tests. When you encounter a substance to which you’re sensitive, like pollen or pet dander, your immune system releases antibodies called immunoglobulin E (IgE) to fight off the intruder. Blood tests measure the amount of IgE antibodies in your system. To complete the test, your phlebotomist will draw blood from your arm and send it to a lab for testing. An elevated number would indicate a sensitivity. It will usually take a few days to get your lab results. Because about 50% to 60% of positive allergy blood tests are false positives,[1] we generally use the test as secondary confirmation of an allergy or if you aren’t able to take a skin test.
The type of test you take will dictate how you prepare, including whether you need to stop taking antihistamines.
When To Stop Taking Antihistamines
Histamine is a chemical your body releases when it encounters an allergen. When your body releases histamine, you’ll develop reactions like hives or itchy eyes. Because antihistamines block these reactions, they can interfere with your skin test results, which rely on visible symptoms.
Antihistamines include all pill, liquid, cream, nasal spray and eye drop varieties. Stop taking all antihistamines five days before your test. If you take other allergy medications, contact us to see if they’re okay to continue.
While it’s safe to take decongestants before an allergy test, you should discontinue all decongestant and antihistamine hybrid medications before your skin test.
You don’t need to stop taking any allergy medication before a blood draw, as the medications don’t typically interfere with antibody production.
How To Control Allergy Symptoms Without Antihistamines
The best way to manage your symptoms when you can’t take antihistamines is to avoid the allergen you suspect is causing them. For example, if you think pollen is at fault, steer clear of Tyrrell Park for a few days.
If you have any questions about preparing for your allergy tests, contact Southeast Texas Ear, Nose & Throat, LLP today to speak to one of our specialists.
[1] Cleveland Clinic. (2024, November 7). Allergy blood test. https://my.clevelandclinic.org/health/diagnostics/allergy-blood-test
