Getting an allergy test typically starts with a visit to your primary care doctor, who can either perform basic testing or refer you to an allergist for more detailed evaluation. The process involves a medical history review, a physical exam, and then one or more types of tests depending on what you might be reacting to. Most testing appointments take under an hour, though some types require multiple visits over several days.
Start With Your Doctor
Your first step is scheduling an appointment with your primary care provider or going directly to an allergist (some insurance plans let you skip the referral). At this visit, expect detailed questions about your symptoms: what happens, when it happens, how long it lasts, whether it runs in your family, and what you’ve already tried. Bring a list of every medication you take, including over-the-counter drugs and supplements, since some of them interfere with testing.
Your doctor will also do a physical exam looking for clues like nasal swelling, skin rashes, or breathing issues. Based on all of this, they’ll decide which type of test makes sense. Not everyone gets the same test or the same number of tests. A person with seasonal sneezing gets a very different workup than someone who broke out in hives after eating shrimp.
For certain situations, a specialist referral is necessary. If you’ve had a severe reaction during surgery, a suspected reaction to antibiotics you may need again, or anaphylaxis from any cause, your doctor will send you to an allergist or immunologist with the tools to investigate safely.
Skin Prick Testing
The skin prick test is the most common allergy test and checks for immediate reactions to as many as 50 substances at once. It’s usually done on the forearm in adults and on the upper back in children. A nurse places tiny drops of allergen extracts on your skin, then lightly scratches or pricks through each drop so a small amount enters the outer layer of skin. It feels like light fingernail scratches, not needle sticks.
After about 15 to 20 minutes, the results are visible. If you’re allergic to a substance, a small raised bump (called a wheal) surrounded by redness appears at that spot. A wheal 3 millimeters or larger in diameter counts as a positive result. The entire appointment usually takes 20 to 40 minutes. Positive skin reactions don’t always mean you’ll have real-world symptoms, though. Depending on the allergen, anywhere from 40% to nearly 90% of positive skin test results line up with symptoms people actually experience when exposed.
Blood Tests
Blood tests measure the level of allergy-related antibodies (called IgE) your immune system produces in response to specific triggers. A standard blood draw is sent to a lab, and results come back in a few days to a week. Blood testing is generally used when skin testing might be unsafe or unreliable. That includes situations where you take medications that can’t be stopped, you have severe eczema or another skin condition covering large areas, or you’ve had a reaction so severe that even the tiny amount used in a skin prick could be risky.
Blood tests are convenient since they require just one visit and no medication changes, but they’re slightly less sensitive than skin prick tests for most allergens. Your doctor may use them alongside skin testing for a fuller picture.
Patch Testing for Skin Reactions
If your issue is a rash that develops where something touches your skin (contact dermatitis from jewelry, fragrances, preservatives, or chemicals), patch testing is the right test. This one requires commitment: small patches containing common allergens are taped to your back, and you wear them for 48 hours. You return to have the patches removed and your skin read for the first time. Then you come back again 48 hours later for a final reading, since true allergic reactions persist or first appear at this five-day mark.
During the entire five days, you can’t shower, get the test site wet, exercise heavily enough to sweat, or apply any steroid cream to your back. It’s not painful, but the scheduling and lifestyle restrictions make it more involved than other allergy tests.
Oral Food Challenges
When skin and blood tests aren’t conclusive for a food allergy, or when your doctor thinks you may have outgrown one, an oral food challenge is the gold standard. You eat gradually increasing amounts of the suspected food under medical supervision, with doses spaced 15 to 30 minutes apart. After the final dose, you’re monitored for about two hours.
This test is always done in a clinical setting with emergency equipment on hand, since allergic reactions up to and including anaphylaxis can occur. Before the challenge, your doctor will make sure you haven’t recently taken systemic steroids (which can mask or confuse results) and that you’re healthy enough to proceed. The result is straightforward: if you react, the allergy is confirmed. If you eat the full amount with no symptoms, you’re cleared to add that food back into your diet.
Medications to Stop Before Testing
Antihistamines are the biggest concern because they suppress the very immune response skin tests are trying to measure. The required washout period depends on the specific drug:
- 7 days before testing: Stop longer-acting antihistamines like cetirizine (Zyrtec), loratadine (Claritin), fexofenadine (Allegra), levocetirizine (Xyzal), and prescription nasal antihistamine sprays.
- 3 days before testing: Stop shorter-acting antihistamines like diphenhydramine (Benadryl), chlorpheniramine, and sleep aids containing antihistamines like Tylenol PM or Unisom. Also stop heartburn medications like famotidine (Pepcid) and cimetidine, which have mild antihistamine effects.
One important exception: if you’re being evaluated for chronic hives, you typically do not need to stop your antihistamines. Your allergist’s office will give you specific instructions when you schedule, so confirm which of your medications need to be paused.
Testing in Children and Infants
Skin prick testing can be done at almost any age. The only real limitation is that it’s rarely performed on infants younger than 6 months. Beyond that, there is no minimum age requirement. Young children are usually tested on their back rather than their forearm since it provides more surface area and is easier to keep still. Blood tests are also an option for children of any age when skin testing isn’t practical.
Skip At-Home Sensitivity Kits
At-home food sensitivity tests, which you can order online and complete with a finger prick, measure a different type of antibody (IgG) than clinical allergy tests (IgE). These IgG levels reflect foods you’ve been eating regularly, not foods your body is reacting to. A high IgG level to a food generally means your immune system has developed tolerance to it, which is the opposite of what the test claims to show.
Multiple professional organizations, including the American Academy of Allergy, Asthma & Immunology, recommend against using these kits. There are no clinical trials showing they accurately identify food sensitivities, and they produce a high number of false positives. People often end up unnecessarily eliminating large groups of foods from their diet based on meaningless results. If you suspect food sensitivities rather than true allergies, a food and symptom journal tracked over several weeks is a more reliable starting point than any mail-order kit.
Insurance and Cost
Most insurance plans, including Medicare, cover allergy testing when it’s deemed medically necessary. That means your doctor has documented symptoms, taken a history, done an exam, and determined that testing is needed to diagnose or treat your condition. The number and type of tests should match your clinical situation. If your doctor orders an unusually large panel, your insurer may require additional justification.
Without insurance, skin prick testing generally costs between $60 and $300 depending on how many allergens are tested. Blood panels can run $200 to $1,000 or more. Calling your insurance company before your appointment to confirm coverage and any referral requirements can save you from unexpected bills.