Over 50 million people in the U.S. have allergies Some experience symptoms like a stuffy nose or itchy eyes, but others have serious reactions that can have terrible health implications. To better understand and manage symptoms, the first step is to undergo allergy testing to determine the root cause or causes of the issue.
In this guide, we’ll talk about the different allergy tests available and which are the best fit for different types of symptoms. Whether you’re looking into your kid’s allergies or your own, it’s helpful to understand all of the details before an appointment with your doctor.
Why Have Allergy Testing Done?
The purpose of having an allergy test is to determine what substances cause an allergic reaction. These reactions could be mild, moderate, or severe and can include a variety of symptoms.
There are two ways to do a basic allergy test: a skin test or a blood test.
Skin Pick Test
- Best used to identify airborne allergens like dust, pollen, mold, or pet dander.
- Also helps narrow down possible food allergens like peanuts, milk, soy, or wheat.
- Determine if you have an allergy to medication or insect venoms like bees or wasps.
- An option if you have a skin condition or hives that could make it difficult to determine skin test results.
- Also used if you are required to take a medication that could prevent a reaction, such as an antihistamine, in a skin test.
- If you have a severe allergic reaction, such as anaphylaxis, a blood test is a safe way to do additional screening.
- If a skin pick test popped positive for nutritional allergies, a blood test to determine food allergies is done as a follow up to help narrow down the specific ones that are causing the reaction.
What to Do Before Your Test
Prior to scheduling allergy testing with your doctor, you’ll want to have a detailed discussion about any prescription and non-prescription medications you’re taking as these can impact your results. You may need to stop taking some medicines, like a daily antihistamine like Zyrtec or Allegra, for several days before a skin test.
Be sure also to ask your doctor for the details of the procedure. It’s helpful to be clear on what will happen, any risks involved, and how you’ll get the results.
Research possible treatment options ahead of time, and talk with your provider about alternatives. For example, if you receive a food allergy diagnosis, it’s important to have a plan for next steps that will allow your body to heal and manage your symptoms.
Factors That Can Impact Allergy Testing
Talk with your doctor about which test type is the right one for you. There are many reasons why you may choose a skin prick test instead of a blood test and vice versa. Below, we discuss a few key points to consider.
If you do exercise that causes excessive sweating or if you have a job or lifestyle that would make it impossible to keep your skin patch dry, this isn’t a good test choice.
Although skin tests are the easiest and most cost-effective method for testing, they won’t be able to diagnose food-specific allergies. Skin tests are more reliable than the alternatives in identifying inhaled allergens, but they are sometimes uncomfortable, especially for children.
While blood tests aren’t affected by any medications you’re on, they are a less sensitive test choice. It’s possible to have a positive reaction to a skin prick, but not see those same results in a blood test.
Blood testing is a more expensive option, but if you have any type of current skin condition, they may be a better way to see accurate results.
6 General Categories of Allergy Testing
Now that we’ve discussed the basic purposes of both skin and blood testing, we’ll go into more detail about the seven different categories of procedures. While there are dozens of varying test types available, these are the most common ones you’ll discuss with your doctor.
We’ll give you specifics on how they’re used, the procedure, and how to prepare for the test.
1. Skin Testing for Allergies
Use: Most commonly used to evaluate environmental or seasonal allergies through inhaled substances, skin testing also produces accurate results for stinging insects, some medications, and can help confirm a general food allergy.
There are two methods for skin testing: prick and intradermal.
In both cases, the suspected allergen is applied to the skin, and your doctor will read your results after 15 minutes of exposure. There are a few differences between the two methods.
In prick skin testing, your doctor may use one or more than one individual solution that has the suspected allergens in it. They prick your skin with a micro needle and then read the reactions 15 minutes later.
The intradermal skin testing method is visually identical; the only difference is that the suspected irritants are placed just beneath the surface of your skin with a small needle. These are also ready to diagnose 15 minutes later.
Which method is right for you is best determined by your doctor.
How to Prepare
Disclose all of the medications you take currently to your doctor and determine which, if any, could affect your test results. Remember, things like sleep aids that contain antihistamines, and some anti-depressants have chemicals that could block the test results. Discontinue these medications for five days prior to your appointment, and don’t begin taking any new drugs during this time.
2. Blood Testing
Use: Blood testing is most commonly used in situations where skin pricks are not appropriate. If you are taking a medication that would affect the results of your skin test, and cannot discontinue using it without compromising your health, a blood test is a good alternative.
Patients with rashes or skin conditions like eczema may also require blood testing to get accurate results. Finally, if you need to whittle down your skin results to a more specific panel, such as in the case of identified food allergies, specific IgE tests may be ordered.
Also, several immune disorders may present with symptoms similar to allergies that are tested through blood. People who have swelling episodes or chronic hives may actually have an immunodeficiency disorder.
3. Lung Function Tests
Asthma is one common symptom of a moderate allergic reaction, and there are lung function or spirometry tests to diagnose it.
During the test, you will inhale deeply and then exhale quickly and forcefully into a device that measures and records your lung function. Expect to repeat this process a minimum of three times to get consistent results.
The spirometer will measure your lung function, and then your doctor can determine your results in the same appointment.
4. Additional Food Allergy Testing Methods
While skin and blood tests can give your doctor some direction on possible food allergies, it’s extremely difficult to get precise results. Most tests provide you with guidance, but further experimentation is required to get to the root of the problem.
One method your doctor may use is a food challenge. Here, you’ll eat a very small, incremental dose of the food that is suspected to cause issues and then be observed and assessed by your physician. They will determine if you have any tolerance for the substance, and also be on hand to assist if you have an adverse reaction.
5. Medication Challenge
If you are someone taking several medications, determining which is causing the issue can be difficult. Just like the example above with a food challenge, in a medication challenge, your doctor will introduce a small amount of a drug that you’re currently avoiding into your system and observe the results. This process happens over time in several incremental steps, and each time the dose is increased there is a period of observation to gauge the effects.
6. Patch Testing
This method of allergy testing is how doctors determine the cause of contact dermatitis.
Defined as a red, itchy rash that you develop as a reaction to a substance you’re allergic to, this condition is extremely common. While it’s not contagious, nor does it have life-threatening implications, it is very uncomfortable for many who suffer from it.
Most commonly, contact dermatitis is a reaction to metal or ingredients in soaps, cosmetics, or laundry detergents.
To determine what is causing the irritation, one or more of the agents are applied to a patch, which is then placed on your back. These patches stay in place for 48-hours, at which time your doctor will remove them. After that, you’ll come back to the office two to five days later to have your results interpreted.
Keep in mind, to get the most accurate diagnosis you’ll need to avoid water and excessive sweating during and following the test.
Once you’ve identified what’s causing the reaction, you can both treat the area appropriately and avoid the substance to prevent further breakouts.