If you have allergies, you’re probably familiar with the ways your immune system broadcasts its general lack of chill. Maybe your nose releases a river of snot, your eyes feel maddeningly scratchy, or your skin erupts with hives.
Whatever the symptoms, allergies are a sign that your immune system is overreacting to a substance. In an effort to protect you, it produces a type of antibody called Immunoglobulin E (IgE) that eventually causes those telltale symptoms, according to the American Academy of Allergy Asthma & Immunology (AAAAI).
But…what if you have no idea what’s setting off your allergies? This is where allergy testing comes in. Allergy testing exposes you to various allergens to gauge your body’s reaction. It can be helpful even if you suspect you know what’s causing your allergies, because you might be wrong. “Some patients may think one thing caused their allergic reaction, but after testing, we find out it was something else,” Princess Ogbogu, M.D., director of allergy and immunology at The Ohio State University Wexner Medical Center, tells SELF.
Ready to dive into allergy testing, but curious about how it’ll go? Here’s what to know about the allergy testing process.
Allergy tests come in three main categories: skin tests, blood tests, and food challenges. We’ll go over what’s involved in each one, plus why you might get this kind of test over another.
Skin testing is the most popular way to test for allergies. This is because skin testing is usually the easiest, least painful option and covers a wide range of allergens (especially those to common airborne substances, like pollen, animal dander, and dust mites), Jonathan A. Bernstein, M.D., an allergist/immunologist and professor of medicine at the University of Cincinnati, tells SELF. Skin testing may also help diagnose food allergies, the Mayo Clinic explains, although these can be less straightforward and might require additional testing.
There are several types of allergy skin tests. Here’s a quick run-down of each:
Skin prick test: Prick testing looks for a pretty immediate reaction to environmental and food-related allergens, Purvi Parikh, M.D., an allergist/immunologist with Allergy & Asthma Network and NYU Langone Health, tells SELF. Though this kind of allergy testing does use needles, the upside is that the needles just barely pierce the surface of your skin. Translation: The prick itself should be pretty painless, Dr. Ogbogu says.
The action typically goes down on your forearm, the Mayo Clinic explains, but you may also get the test performed on your back. After a health care professional cleans the testing site with alcohol, they’ll draw marks on your skin and put drops of various allergen extracts next to each mark. Then they’ll puncture your skin with a needle to introduce the extract into your system. They’ll also apply two other things to your skin to see if it’s reacting normally: histamine, which causes a skin response in most people, and glycerin or saline, which doesn’t cause a reaction in most people.
About 15 minutes after the initial injections, the health care professional performing the testing will examine how your skin’s handling the intrusions. If you have an allergic reaction, you’ll likely have a red, raised, itchy bump that resembles a mosquito bite, the Mayo Clinic says. They’ll take note of the results and clean your arm or back with alcohol to get rid of the marks they drew.
How long you’ll have allergy symptoms after your test can vary, but in general, the reaction might last for a few hours, Dr. Parikh says. However, to help the symptoms clear up sooner, you can usually take an antihistamine right after a doctor has recorded the results of any kind of allergy testing, she says. To be certain, ask your doctor how soon after testing you can take allergy drugs.
Skin injection test: This involves using a needle to inject a small amount of allergen extract into the skin on your arm, the Mayo Clinic says. Unlike a prick test, the skin injection test goes a little deeper, Dr. Parikh says, so you may feel a pinch when the needle enters your skin.
This is typically done if your doctor thinks you have a specific allergy but your skin prick test was negative, Dr. Parikh says, especially if they think you might have a serious allergy to something like insect venom or penicillin, according to the Mayo Clinic. (False negatives are possible for various reasons, like if you were on a medication that suppressed an allergic reaction—more on that in a bit.)
Just like the skin prick test, a health professional will examine your skin after about 15 minutes and record the results.
Patch test: For this kind of testing, you’ll wear patches containing allergens for around 48 hours to see how your skin reacts, the Mayo Clinic explains. During that time, your doctor will likely advise you to avoid showering and doing things that cause heavy sweating. Once you go back to the doctor, they will remove the patches and inspect the areas in question to see if you’ve had a reaction.
Patch testing is usually conducted to see what might be causing an issue like contact dermatitis (an allergic skin reaction that involves an itchy, inflamed rash) or eczema (a condition that can cause persistently dry, irritated, rash-ridden skin). These reactions can take more time to develop than reactions to something like pollen or dust mites, hence the days-long period of wearing the patches before a professional examines the results, Dr. Parikh explains.
Your doctor may recommend that you get a blood test if you’ve had a severe allergic reaction in the past, take necessary medications that might interfere with your test results, or have a condition like severe eczema that makes it hard to carry out skin testing, the Mayo Clinic says. Blood tests are generally good for these cases because they don’t expose you to an allergen (which raises the risk that you’ll have a reaction) or require you to stop medication that you may need to function normally, Dr. Bernstein says.
Blood tests look for the presence of those IgE antibodies in your system, but they aren’t done as often as skin tests because they can be less sensitive. Also, even though many insurance plans cover at least some allergy testing, blood tests tend to be more expensive, so you might have to front more of the cost.
If you’re having a blood test, your doctor will clean your skin with alcohol, draw your blood with a needle, put a bandage on the injection site, and send you on your way, Dr. Bernstein says. After that, they should call you in a few days when they have your results.
With a challenge test, you’ll inhale or ingest a very small amount of an allergen under a doctor’s supervision. This is usually done with potential food allergies to determine the level of your allergy, especially if skin and blood tests were inconclusive, the AAAAI says. It can also be useful when looking for medication allergies.
The day of the test, your doctor might tell you to avoid eating very much (or at all). Once you go in for your appointment, they’ll have you start consuming tiny amounts of whichever substance it seems may cause your reactions, the AAAAI explains. (Discuss with them beforehand if you should bring the food/medication or if they’ll provide it.) You’ll continue eating in intervals, usually around every 15 to 30 minutes, to allow time for a reaction to develop, although this depends on the specific allergy and how long it usually takes symptoms to start.
If you do start getting symptoms such as hives, a tingling mouth, or stomach pain that point to this kind of allergy, your doctor can treat them promptly with drugs such as antihistamines.
It is technically possible to have a more severe allergic reaction during allergy testing, but this isn’t likely, Dr. Bernstein says. Even if it did happen, they should have emergency medications on hand to ward off anything life-threatening such as anaphylactic shock (a potentially fatal reaction that makes it impossible to breathe). If you’re worried, ask how your doctor would handle a severe allergic reaction before testing begins.
Whether you do or don’t have allergy symptoms during challenge testing, your doctor may want you to stick around for a few hours after the test to watch for a delayed reaction or make sure any symptoms you do experience are under control, the AAAAI explains.
There’s a chance certain medications can interfere with allergy testing results, so have a thorough chat with your doctor about any drugs you’re taking beforehand.
Some medications can suppress allergic reactions and prevent skin tests in particular from giving accurate results, Dr. Ogbogu says. These include prescription antihistamines, OTC antihistamines, tricyclic antidepressants, some heartburn medications, and certain asthma drugs. When it comes to challenge tests, antihistamines in particular can affect the results.
If possible, your doctor may ask you to stop taking these kinds of drugs (or swap them for a different kind) in the time leading up to your skin or challenge allergy testing. If you’re not able to do that, they may opt to have you do a blood test instead since that makes it easier to continue taking your usual medication.
Once you get your results, your doctor should sit down with you and figure out a treatment plan.
Along with the results of your allergy tests, your doctor will usually consider your medical history to help confirm what you’re touching, breathing in, or eating that is causing a reaction, the Mayo Clinic explains.
That medical history component is key. “It’s important to recognize that a positive test doesn’t mean someone has an allergy,” Dr. Berinstein says. “It still has to correlate with the patient and their history of being exposed.” It’s possible that, due to antibodies present in your system, your body is sensitive enough to react to something during an allergy test. But if you don’t actually have a history of symptoms when you encounter that substance in the wild, you don’t technically have the allergy. For instance, if you get an itchy, red bump in reaction to pine tree pollen but have never had an issue being around Christmas trees, your doctor probably isn’t going to stress about that, Dr. Berinstein says.
But if you really are allergic to something, coming up with a solid course of treatment can ease your struggles. That may mean learning how to avoid foods you’re allergic to and discussing medications that could help manage your allergy when, say, the pollen count is high. If you have a severe allergy, you’ll figure out a plan for managing issues such as anaphylaxis, like carrying an EpiPen.
This is a lot of information, so here’s the most important part to remember: Allergy testing isn’t the most delightful way to spend your time, but it’s often fairly painless and, more importantly, can offer answers that make your life so much better.