During allergy skin tests, your skin is exposed to suspected allergy-causing substances (allergens) and is then observed for signs of an allergic reaction.
Along with your medical history, allergy tests may be able to confirm whether a particular substance you touch, breathe or eat is causing symptoms.
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Why it's done
Information from allergy tests may help your doctor develop an allergy treatment plan that includes allergen avoidance, medications or allergy shots (immunotherapy).
Allergy skin tests are widely used to help diagnose allergic conditions, including:
- Hay fever (allergic rhinitis)
- Allergic asthma
- Dermatitis (eczema)
- Food allergies
- Penicillin allergy
- Bee venom allergy
Skin tests are generally safe for adults and children of all ages, including infants. In certain circumstances, though, skin tests aren't recommended. Your doctor may advise against skin testing if you:
- Have ever had a severe allergic reaction. You may be so sensitive to certain substances that even the tiny amounts used in skin tests could trigger a life-threatening reaction (anaphylaxis).
- Take medications that could interfere with test results. These include antihistamines, many antidepressants and some heartburn medications. Your doctor may determine that it's better for you to continue taking these medications than to temporarily discontinue them in preparation for a skin test.
- Have certain skin conditions. If severe eczema or psoriasis affects large areas of skin on your arms and back — the usual testing sites — there may not be enough clear, uninvolved skin to do an effective test. Other skin conditions, such as dermatographism, can cause unreliable test results.
Blood tests (in vitro immunoglobulin E antibody tests) can be useful for those who shouldn't or can't undergo skin tests. Blood tests aren't used for penicillin allergy.
In general, allergy skin tests are reliable for diagnosing allergies to airborne substances, such as pollen, pet dander and dust mites. Skin testing may help diagnose food allergies. But because food allergies can be complex, you may need additional tests or procedures.
- Acute sinusitis
- Alcohol intolerance
- Alpha-gal syndrome
- Bee sting
- Burning mouth syndrome
- Chronic hives
- Chronic sinusitis
- Dust mite allergy
- Egg allergy
- Eosinophilic esophagitis
- Food allergy
- Hay fever
- Latex allergy
- Lichen planus
- Milk allergy
- Nasal polyps
- Nickel allergy
- Nonallergic rhinitis
- Oral lichen planus
- Peanut allergy
- Penicillin allergy
- Pet allergy
- Shellfish allergy
- Allergy tests
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The most common side effect of skin testing is slightly swollen, red, itchy bumps (wheals). These wheals may be most noticeable during the test. In some people, though, an area of swelling, redness and itching may develop a few hours after the test and remain for a couple of days.
Rarely, allergy skin tests can produce a severe, immediate allergic reaction, so it's important to have skin tests performed at an office where appropriate emergency equipment and medications are available.
How you prepare
Before recommending a skin test, your doctor will ask you detailed questions about your medical history, your signs and symptoms, and your usual way of treating them. Your answers can help your doctor determine if allergies run in your family and if an allergic reaction is most likely causing your symptoms. Your doctor may also perform a physical examination to search for additional clues about the cause of your signs and symptoms.
Medications can interfere with results
Before scheduling a skin test, bring your doctor a list of all of your prescription and over-the-counter medications. Some medications can suppress allergic reactions, preventing the skin testing from giving accurate results. Other medications may increase your risk of developing a severe allergic reaction during a test.
Because medications clear out of your system at different rates, your doctor may ask that you stop taking certain medications for up to 10 days. Medications that can interfere with skin tests include:
- Prescription antihistamines, such as hydroxyzine (Vistaril).
- Over-the-counter antihistamines, such as loratadine (Claritin, Alavert), diphenhydramine (Benadryl), chlorpheniramine, cetirizine (Zyrtec Allergy) and fexofenadine (Allegra).
- Tricyclic antidepressants, such as nortriptyline (Pamelor) and desipramine (Norpramin).
- Certain heartburn medications, such as cimetidine (Tagamet) and ranitidine.
- The asthma medication omalizumab (Xolair). This medication can disrupt test results for six months or longer even after you quit using it. For comparison, most medications affect results for days to weeks.
What you can expect
Skin testing is usually done at a doctor's office. A nurse generally administers the test, and a doctor interprets the results. Typically, this test takes about 20 to 40 minutes. Some tests detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests detect delayed allergic reactions, which develop over a period of several days.
Skin prick test
Positive reaction to allergy test
Positive reaction to allergy test
A small area of swelling with surrounding redness (arrow) is typical of a positive skin prick test for allergy.
A skin prick test, also called a puncture or scratch test, checks for immediate allergic reactions to as many as 50 different substances at once. This test is usually done to identify allergies to pollen, mold, pet dander, dust mites and foods. In adults, the test is usually done on the forearm. Children may be tested on the upper back.
Allergy skin tests aren't painful. This type of testing uses needles (lancets) that barely penetrate the skin's surface. You won't bleed or feel more than mild, momentary discomfort.
After cleaning the test site with alcohol, the nurse draws small marks on your skin and applies a drop of allergen extract next to each mark. He or she then uses a lancet to prick the extracts into the skin's surface. A new lancet is used for each allergen.
To see if your skin is reacting normally, two additional substances are scratched into your skin's surface:
- Histamine. In most people, this substance causes a skin response. If you don't react to histamine, your allergy skin test may not reveal an allergy even if you have one.
- Glycerin or saline. In most people, these substances don't cause any reaction. If you do react to glycerin or saline, you may have sensitive skin. Test results will need to be interpreted cautiously to avoid a false allergy diagnosis.
About 15 minutes after the skin pricks, the nurse observes your skin for signs of allergic reactions. If you are allergic to one of the substances tested, you'll develop a raised, red, itchy bump (wheal) that may look like a mosquito bite. The nurse will then measure the bump's size and record the results. Next, he or she will clean your skin with alcohol to remove the marks.
Skin injection test
You may need a test that uses a needle to inject a small amount of allergen extract just into the skin on your arm (intradermal test). The injection site is examined after about 15 minutes for signs of an allergic reaction. Your doctor may recommend this test to check for an allergy to insect venom or penicillin.
Patch testing is generally done to see whether a particular substance is causing allergic skin inflammation (contact dermatitis). Patch tests can detect delayed allergic reactions, which can take several days to develop.
Patch tests don't use needles. Instead, allergens are applied to patches, which are then placed on your skin. During a patch test, your skin may be exposed to 20 to 30 extracts of substances that can cause contact dermatitis. These can include latex, medications, fragrances, preservatives, hair dyes, metals and resins.
You wear the patches on your arm or back for 48 hours. During this time, you should avoid bathing and activities that cause heavy sweating. The patches are removed when you return to your doctor's office. Irritated skin at the patch site may indicate an allergy.
Before you leave your doctor's office, you'll know the results of a skin prick test or an intradermal test. A patch test may take several days or more to produce results.
A positive skin test means that you may be allergic to a particular substance. Bigger wheals usually indicate a greater degree of sensitivity. A negative skin test means that you probably aren't allergic to a particular allergen.
Keep in mind, skin tests aren't always accurate. They sometimes indicate an allergy when there isn't one (false-positive), or skin testing may not trigger a reaction when you're exposed to something that you are allergic to (false-negative). You may react differently to the same test performed on different occasions. Or you may react positively to a substance during a test but not react to it in everyday life.
Your allergy treatment plan may include medications, immunotherapy, changes to your work or home environment, or dietary changes. Ask your doctor to explain anything about your diagnosis or treatment that you don't understand. With test results that identify your allergens and a treatment plan to help you take control, you'll be able to reduce or eliminate allergy signs and symptoms.
By Mayo Clinic Staff
Jan. 06, 2022
Skin tests are usually accurate. But, if the dose of allergen is large, even people who are not allergic will have a positive reaction. Your provider will consider your symptoms and the results of your skin test to suggest lifestyle changes you can make to avoid substances that may be causing your symptoms.What is the most accurate skin allergy test? ›
Skin prick testing (SPT) is the preferred testing method for true food allergy. It is safe for most patients—even infants—and it can be done during a regular clinic visit. Results are available immediately after the test, so you will be able to discuss the results with your allergist at the same visit.How accurate are skin tests for food allergies? ›
About 50-60 percent of all SPTs yield “false positive” results, meaning that the test shows positive even though you are not really allergic to the food being tested. If you are taking antihistamines, it's important to keep in mind that they can interfere with skin tests.Is a skin test or blood test more accurate for allergies? ›
Generally speaking, skin tests are more sensitive than blood tests, meaning they are more likely to detect allergies that a blood test may miss. Skin tests also require less wait time, as results are typically delivered in 15-20 minutes, rather than the one to two week wait time of blood tests.Can you trust allergy tests? ›
None of these have any scientific validity at all. Only a blood sample can be used to identify an allergy. A blood test for IgE antibodies can be helpful in diagnosing an allergy, but IgE levels vary enormously between individuals and are also specific to particular things (like pollen, or foodstuffs).Are allergy tests 100 accurate? ›
Allergy blood tests may not always be accurate. Sometimes the results may say you have an allergy when you actually don't (also known as a false positive). This may happen if your body is having a slight reaction to substances in certain foods that you may have eaten before the test.At what age is allergy testing accurate? ›
If your child has adverse reactions to certain foods, allergy testing is important to do for their safety. You can have your child tested at any age, however, skin tests generally aren't done in children under the age of 6 months. Allergy tests may be less accurate in very young children.What should you not do before an allergy test? ›
Do not take over the counter antihistamines (Benadryl, cold & sinus medications, sleep aids such as Tylenol PM) 7 days before the test. Do not take medications such as Tagamet, Pepcid, or Zantac 1 day prior to testing, as these contain a form of antihistamine. Do not take a tricyclic antidepressant medication.How often should you get allergy skin test? ›
Answer. Two years between allergy tests is reasonable – there are no limitations to the frequency of testing. But you can talk with your allergist about whether retesting is necessary. Allergists will typically recommend retesting for symptomatic or therapeutic reasons.Is allergen test worth it? ›
Most medical experts agree that at-home food sensitivity tests are not worth your money. Instead, consider taking an at-home food allergy test or meeting with a doctor or registered dietitian to identify the cause of your unwanted symptoms.
A skin prick test can determine your reaction to a particular food. In this test, a small amount of the suspected food is placed on the skin of your forearm or back. A doctor or another health care provider then pricks your skin with a needle to allow a tiny amount of the substance beneath your skin surface.What are the 3 most common food intolerances? ›
Some of the most common food intolerances include gluten, dairy, FODMAPs and histamine. There is also a wide range of less common food intolerances .What is the difference between a skin test and a patch test? ›
What Is a Skin Patch Test? The skin patch test differs from a skin prick test in that it focuses on contact skin allergies as opposed to reactions from food consumption or airborne allergens. Skin prick test results are delivered within an hour, but skin patch results take about 48-96 hours.What does a negative skin allergy test look like? ›
The positive control, usually a histamine solution, should become itchy within a few minutes and then become red and swollen with a “weal” in the centre. The negative control, usually a saline solution should show no response.What does a skin test specifically detect in allergy testing? ›
An allergy skin test is used to diagnose certain allergies. The test can show which substances (allergens) are causing your allergic reaction. These substances may include pollen, dust, molds, and medicines such as penicillin. The tests are not usually used to diagnose food allergies.Can a dermatologist tell you if you're allergic to something? ›
Some dermatologists offer extensive patch testing. This means that they can test you for many different substances that could be causing your allergic skin reaction. To find a dermatologist who offers patch testing: Go to Find a dermatologist.What if I test negative for allergies but still have symptoms? ›
If you tested negative to all 45 allergens, then you likely have either a sensitivity to a less common allergen or you have nonallergic rhinitis, which just seems like an allergy. At any rate, you certainly can get on with treatment. A combination of nasal sprays, antihistamines and eye drops (if needed) should help.