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Direct Answer
Preparation for allergy testing depends on the test type. For skin prick testing, you must stop antihistamines 3–7 days before the appointment (depending on the specific medication), avoid certain other drugs, and eat normally. For allergy blood testing (specific IgE)—the method HeyAllergy uses via telemedicine—there are essentially no medication restrictions. You do not need to stop antihistamines, and you can eat and drink normally before your blood draw.
Preparation Checklist: Skin Prick Testing vs. Blood Testing
Which Medications to Stop Before Skin Testing
If your allergist has ordered skin prick testing (not blood testing), the following medications must be stopped because they block the histamine response the test measures. Always confirm with your prescribing doctor before stopping any medication.
Medications You Do NOT Need to Stop
These medications are safe to continue before both skin testing and blood testing:
- Nasal corticosteroid sprays (fluticasone/Flonase, mometasone/Nasonex, budesonide/Rhinocort) — These reduce nasal inflammation but do not block the skin histamine response.
- Asthma inhalers (albuterol, fluticasone/salmeterol, budesonide/formoterol) — Continue all asthma medications. Stopping them before testing is dangerous and unnecessary.
- Leukotriene modifiers (montelukast/Singulair) — These block a different inflammatory pathway (leukotrienes, not histamine) and do not interfere with skin testing.
- Decongestants (pseudoephedrine/Sudafed, phenylephrine) — These work on blood vessels, not histamine receptors.
- Oral corticosteroids (prednisone) — Short courses do not significantly suppress skin test results. Long-term use may require discussion with your allergist.
What to Eat (and What to Skip) Before Allergy Testing
For Blood Testing
Eat and drink whatever you normally would. Allergy blood tests measure IgE antibody levels in your serum, and food intake does not change these levels. Staying well-hydrated actually helps—it makes veins easier to find and the blood draw faster. Drink a glass of water before your lab appointment.
For Skin Prick Testing
Same rule: eat a normal meal before your appointment. Skin testing can take 30–60 minutes, and you will be sitting still while waiting for skin reactions to develop. Arriving hungry makes the experience less comfortable. There are no foods that interfere with skin test accuracy.
For Food Allergy Testing Specifically
If you suspect a specific food allergy and are being tested for it, you do not need to eat or avoid that food before the test. Both skin and blood tests detect pre-existing IgE antibodies—eating or not eating the suspected food on test day does not change your antibody levels.
What to Bring to Your Allergy Appointment
For a Telemedicine Visit (HeyAllergy)
- Complete medication list — Names, doses, and how often you take each one. A photo of your medication bottles is perfect.
- Insurance card — Front and back photos. HeyAllergy accepts Medicare and most major PPO plans.
- Symptom notes — When did symptoms start? Which months are worst? What makes them better or worse? What have you tried? Write this down before the visit so you do not forget details.
- Family allergy history — Do parents, siblings, or children have allergies, asthma, or eczema? Family history helps determine your risk profile.
- Previous test results — If you have had allergy testing before (skin or blood), bring those results. Even old results help your allergist track changes in your sensitization pattern.
- A quiet, well-lit space — For your secure video consultation. Good lighting helps your allergist see skin conditions or nasal anatomy during the virtual exam.
For an In-Person Skin Test Visit
Everything listed above, plus:
- Short-sleeved or loose-fitting shirt — Skin prick testing is typically done on the forearms or back. Easy access to these areas speeds up the process.
- Something to do for 15–20 minutes — After the allergen pricks are applied, you wait 15–20 minutes for reactions to develop. Bring a book, phone, or headphones.
- A driver (if taking hydroxyzine or similar) — If you were taking a sedating antihistamine and just stopped it, you may still have residual drowsiness. Consider having someone else drive.
How HeyAllergy’s Telemedicine Approach Simplifies Preparation
HeyAllergy uses allergy blood testing (specific IgE panels) ordered through a telemedicine consultation with a board-certified allergist. This approach eliminates most of the preparation complexity:
- No medication stops required — Take your antihistamines, nasal sprays, and all other medications as usual. Nothing needs to change.
- No fasting — Eat and drink normally before your lab visit.
- No in-office wait time — Your video consultation with the allergist is separate from the blood draw. The consultation happens from your home; the blood draw happens at a convenient local lab on your schedule.
- Comprehensive panels — Your allergist orders testing for the specific environmental allergens endemic to your geographic location—tree, grass, weed, mold, dust mite, and pet dander allergens relevant to where you live.
- Results lead directly to treatment — Once results are back (3–7 business days), your allergist reviews them with you and—if appropriate—formulates your customized HeyPak® allergy drops based on exactly which allergens you tested positive for.
Common Preparation Mistakes That Affect Test Results
Mistake 1: Taking Antihistamines Too Close to a Skin Test
This is the most common issue. Even one dose of cetirizine taken 3 days before a skin test can suppress the wheal-and-flare response, leading to false negatives—where the test says you are not allergic when you actually are. If you accidentally take an antihistamine, tell your allergist. They may reschedule or switch to a blood test.
Mistake 2: Not Mentioning OTC Products with Hidden Antihistamines
Many nighttime cold medicines, sleep aids, and combination products contain diphenhydramine or doxylamine. Patients often do not think of these as “antihistamines” because they take them for sleep or cold symptoms. Always bring a list of everything you take—including OTC products and supplements.
Mistake 3: Stopping Asthma Medications Before Testing
Some patients mistakenly stop their asthma inhalers before allergy testing, thinking all medications need to be stopped. This is dangerous. Asthma inhalers do not affect allergy test results, and stopping them can trigger an asthma attack—especially during the allergy appointment itself. Never stop asthma medications unless your allergist specifically instructs you to.
Mistake 4: Not Knowing Your Symptom Timeline
Your symptom history is often more valuable than the test itself. If you cannot describe when your symptoms are worst, what environments trigger them, or how long you have had them, your allergist has less information to guide testing and treatment decisions. Spend 10 minutes before your appointment writing down your symptom pattern.
When to See an Allergist
Book a telemedicine allergy consultation if:
- You have had nasal congestion, sneezing, itchy eyes, or post-nasal drip for more than 4 weeks and OTC medications are not providing adequate relief
- You are not sure what you are allergic to and want specific testing to identify your triggers
- You have been taking daily antihistamines for months or years and want a long-term solution that addresses the root cause rather than just masking symptoms
- You have symptoms that are getting worse each year, suggesting increasing sensitization
- You want to start sublingual immunotherapy (SLIT) but need allergy testing first to identify which allergens to include in your custom formula
- You have had allergy testing before but it was more than 3–5 years ago and your symptoms have changed
- You have been putting off allergy testing because you thought you had to stop all your medications—with blood testing, you do not
Frequently Asked Questions
Do I need to stop taking Zyrtec before allergy testing?
It depends on the test type. For skin prick testing, yes—stop cetirizine (Zyrtec) at least 5–7 days before the test, as it suppresses the histamine response the test measures. For blood testing (specific IgE), no—antihistamines do not affect blood test results because the test measures antibody levels in your serum, not a skin histamine reaction. HeyAllergy uses blood testing for telemedicine patients, so you can continue all medications including Zyrtec.
Can I eat before allergy testing?
Yes. Allergy testing—both skin prick and blood testing—does not require fasting. Eat a normal meal before your appointment. Staying well-hydrated is especially helpful before a blood draw, as it makes veins easier to find. The only rare exception is if your allergist specifically requests fasting for a specialized test, which they would tell you in advance.
What happens during an allergy blood test?
A standard blood draw (one needle stick, one or two tubes of blood, about 5 minutes) at a local lab. The blood is sent to a reference laboratory where it is tested against a panel of specific allergens chosen by your allergist based on your symptoms and geographic location. Results are typically available in 3–7 business days. Your allergist reviews results with you during a follow-up telemedicine visit and builds your treatment plan.
Is skin testing or blood testing more accurate?
Both are well-validated and clinically reliable when interpreted by a board-certified allergist alongside your symptom history. Skin prick testing has slightly higher sensitivity (fewer false negatives) for some allergens, while blood testing has the advantage of no medication interference, no risk of allergic reaction during testing, and can test for a broader panel of allergens in a single draw. The AAAAI considers both appropriate for diagnosing allergic sensitization. Your allergist will recommend the best option based on your specific situation.
How long does allergy testing take?
For blood testing: the telemedicine consultation is typically 15–30 minutes, and the blood draw at the lab takes about 5–10 minutes. For skin prick testing: the in-office appointment is typically 45–60 minutes, including application of allergen extracts (5–10 minutes), waiting for reactions to develop (15–20 minutes), and reading and discussing results with the allergist.
What happens after allergy testing?
Your allergist reviews results with you and creates a personalized treatment plan. This may include allergen avoidance strategies, prescription medications (nasal corticosteroids, antihistamines), and—for long-term immune desensitization—sublingual immunotherapy (SLIT) with HeyPak®. HeyPak drops are customized to your exact test results, targeting the specific allergens your immune system reacts to. Treatment typically shows results within 3–6 months, with 3–5 years recommended for lasting relief.
Author, Review and Disclaimer
Author: Krikor Manoukian, MD, FAAAAI, FACAAI — Board-Certified Allergist/Immunologist
Bio: Dr. Manoukian is a board-certified allergist/immunologist with over 20 years of experience. He leads HeyAllergy’s clinical team and specializes in telemedicine-enabled allergy care and personalized sublingual immunotherapy programs.
Medical Review: HeyAllergy Clinical Team (Board-Certified Allergists/Immunologists)
Disclaimer: This article is educational and not a substitute for personalized medical advice. Always follow your specific allergist’s instructions regarding medication changes before testing. Do not stop any prescribed medication without consulting your prescribing physician.
References
- Bernstein IL, et al. Allergy Diagnostic Testing: An Updated Practice Parameter. Annals of Allergy, Asthma & Immunology. 2008;100(3 Suppl 3):S1-S148.
- AAAAI, Allergy Testing Overview. AAAAI
- Cox L, et al. Allergen Immunotherapy: A Practice Parameter Third Update. Journal of Allergy and Clinical Immunology. 2011;127(1 Suppl):S1-S55.
- NIAID Guidelines for the Diagnosis and Management of Food Allergy in the United States. NIH/NIAID
