Thursday, April 18, 2024
HomeSkinAre Allergy Skin Tests Reliable

Are Allergy Skin Tests Reliable

The Allergy Testing Procedure

Diagnosing Allergies: Reliable Approaches to Testing – Dr Dean Tey | Ausmed Lectures

Skin testing is a simple series of tiny scratches made on your back. Staff uses a small instrument similar to a plastic toothpick, which contains trace amounts of a single allergen, such as mold, pollen, dust mite, and pet dander to perform the allergy test. When the results are positive, a small reaction on the skin occurs, usually within 20 minutes. This reaction is generally a small bump, similar to a mosquito bite, and may cause some itchiness. A bump or reaction indicates that you are allergic to that specific trigger. Following the scratch test on the back, some patients may also receive intradermal testing, where a small amount of the allergen is injected under the skin of the arm to see if it causes a reaction.

Here is a video explaining the testing and immunotherapy process we show to patients after they are tested:

Warning: Food Allergy Blood Tests Sometimes Unreliable

–Doctors urge caution in diagnosis based on test results

Blood tests are becoming an increasingly popular tool in the diagnosis of food allergies, but a study led by scientists at Johns Hopkins Childrens Center reports that some tests are more accurate than others and that too-heavy reliance on blood tests alone to predict allergic reactions may not be a good idea.

Unlike food challenge testing in which people thought to have a food allergy are fed small amounts under a doctors supervision to directly measure an actual allergic reaction blood tests measure IgE antibodies, immune system chemicals involved in allergic reactions.

In a study of the three most common commercial tests, the Johns Hopkins research concluded that some tests are more accurate than others.

In the study, researchers sent patient blood samples with already-known levels of antibodies to either soy or peanut to labs using the three most popular systems.

They discovered substantial differences in the tests ability to detect the antibodies, as well as to accurately measure the amount of antibodies, according to a report in the July 15 issue of Annals of Asthma, Allergy & Immunology.

The differences we saw in sensitivity and accuracy are clearly a red flag because reliance on results may lead to a wrong diagnosis, says the studys lead author, Robert Wood, M.D., director of Allergy and Immunology at the Johns Hopkins Childrens Center.

What Is A Hydrolyzed Diet

A prescription diet where the protein has been enzymatically broken down into small fragments that, IN THEORY, the body DOES NOT react to. Many veterinarians believe hydrolyzed diets are the best and guaranteed to work but, in veterinary medicine we only have partially hydrolyzed products they are not 100% hydrolyzed, and therefore they can still elicit reactions. DCA sees many food allergic pets fail to improve with these types of diets. Studies have shown that 20-50% of food allergic pets can react to hydrolyzed diets. For these reasons, we recommend Rayne Nutrition!

Recommended Reading: Cetirizine And Fexofenadine Together

Which Allergy Test Is Most Accurate

Different allergy tests are more accurate for testing separate allergens. Skin prick tests work best for identifying environmental and some food allergies. Patch tests are more accurate in identifying chemical allergies. Intradermal testing is more accurate in identifying drug allergies. Blood testing is best for testing common environmental allergies. Elimination testing is more accurate in identifying food allergies. Provocation testing is also best used to confirm a food allergy. Ask your allergist which test is best for you.

How Strict Does The Food Trial Need To Be

Kids Under 7: Allergy Test

Completely strict! If a human had peanut allergies, would they eat something with just a little amount of penauts? How about just 1 single peanut? No other flavored medications, treats, supplements, or monthly flavored preventatives , should be given during the food trial. A substitute, non-flavored, or topical option should be recommended. We see food trial failures due to flavored medications daily, because veterinarians overlook this little detail!

Recommended Reading: Allergic Reaction Lip Blisters

After 35 Hours Of Research And Testing My Recommendation Is:

  • Food allergens
  • Allergic reactions on materials

Each lab uses different techniques to perform the test, and these techniques may vary in accuracy and clinical relevance, of course.

As said, blood allergy tests can also determine food allergies and allergic reactions to materials like cotton or nylon, but this test is less reliable than skin allergy testing.

Pros and cons

Blood allergy testing is convenient, and it can easily be performed in general practice. Also, patients do not have to be sedated or shaved, which is great since this might be stressful for dogs. All that is needed for this procedure is a single blood sample.

However, there are drawbacks to blood allergy testing.

These tests are very often associated with false positives that cannot be confirmed through intradermal skin testing. Positive allergy test results have also been observed with no evidence of atopic dermatitis, and usually, allergen-specific IgE does not correlate with the real clinical picture and severity of the allergic reaction

These findings put a shade on the validity of blood allergy testing. However, the patients treated on the basis of blood allergy testing often report clinical improvement, so blood testing can’t be ruled out as a bad decision, but skin testing will always be more accurate.

What Happens If I Have An Allergy

Depending on the allergy, your healthcare provider may recommend one or more of these steps:

  • Minimize exposure to allergens: Avoid ones that cause severe reactions, such as latex or certain foods.
  • Take daily allergy medications: Antihistamines can prevent or reduce allergic rhinitis and other symptoms.
  • Get allergy shots: This type of immunotherapy can decrease the immune systems response to certain allergens like pet dander. You should get allergy shots for three to five years to experience maximum benefit. Allergy shots can be costly, but they often provide long-lasting relief, even after the shot series is completed.
  • Have a medical alert card: A card or medical alert jewelry lets others know about your severe allergy. It tells them you could have an anaphylactic response to peanuts, bee stings or other allergens.
  • Carry an epinephrine injection: Keep this medicine with you at all times if youre at risk for an anaphylactic allergic reaction.

A note from Cleveland Clinic

Allergic reactions can range from annoying congestion to life-threatening anaphylactic shock. Allergy tests can identify substances that cause these types of allergic reactions. There are different allergy tests. Your healthcare provider will choose the best test for you based on symptoms and potential allergy triggers. If you have allergies, you can take steps to get symptom relief.

Recommended Reading: Allergies And Vomiting

What Kind Of Food Allergy Testing Is Actually Reliable

Food allergies are a common scapegoat for all kinds of health problems but not all food allergy tests are accurate. A lot of people today buy allergy tests directly from the manufacturer and get back results showing that theyre allergic to all kinds of things. But most of these tests are based on IgG testing, a method that many different studies have shown to be totally inaccurate.

This isnt just an academic problem. If you actually have a health problem that needs treatment, it wont help to start avoiding some random food based on an inaccurate test claiming youre allergic to it. In fact, it might hurt because it could distract you from finding the real cause of your problem.

In that spirit, heres a look at which food allergy tests are actually reliable and which ones arent.

Intradermal Allergy Testing: How Its Done

Why Choose Allergy Skin Testing

Intradermal allergy testing involves injecting small quantities of allergens into the patients skin. This procedure is typically performed under sedation or general anesthesia, following a strict monitoring protocol. Approximately 40-60 injections are given in a single area of the body with a small sample of each allergen injected just under the skin.

A positive response to an allergen appears as a visible swelling, which looks like a hive. This swelling forms at the injection site and is typically observed within 20 minutes of injection. If such a swelling does not occur, a patient is assumed to not be allergic to that specific allergen.

  • Blog
  • What is Skin Allergy Testing
  • Are you having a runny nose, itchy eyes, swollen face, and breathlessness? Welcome to the world of allergy.

    Allergic reactions are a common concern for people. You would be amazed to know over 50 million people in the United States have different types of allergy, as reported by the American College of Allergy, Asthma & Immunology .

    You may have an allergic reaction after inhaling, eating, or touching an allergen substances that cause an allergic reaction. Allergy testing is a procedure where the health care provider determines which substances responsibly instigate allergic reactions in you.

    Also Check: Non Drowsy Allergy

    Other Skin Testing Methods

    Intradermal testing should not be used to test for allergy to inhalants or foods. Instradermal testing was used in the past, however it is less reliable than skin prick testing, and causes much greater discomfort. Intradermal skin testing may be used to test for allergies to antibiotic drugs or stinging insect venom, when greater sensitivity is needed.

    What To Expect When You Have The Test

    Before youre given a skin prick test, your doctor will talk with you. Youll discuss your health history, your symptoms, and the types of triggers that seem to set off your allergies. Your doctor will use this information to determine which allergens to use in testing. Your doctor may test you for as few as three or four substances or as many as 40.

    The test is usually performed on the inside of your arm or on your back. Typically, a nurse administers the test, and then your doctor reviews your reactions. Testing and interpreting the results usually takes less than an hour but the time depends on the number of allergens being tested.

    Also Check: Allergies And Brain Inflammation

    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 .
    • Over-the-counter antihistamines, such as loratadine , diphenhydramine , chlorpheniramine, cetirizine and fexofenadine .
    • Tricyclic antidepressants, such as nortriptyline and desipramine .
    • Certain heartburn medications, such as cimetidine and ranitidine.
    • The asthma medication omalizumab . 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.

    If I Am Really Allergic To A Food Why Do The Skin Prick And Blood Tests Not Always Show It

    Allergy test

    There may be several reasons why allergy tests are negative when a person is actually allergic. This is why a series of tests leading up to an oral challenge is sometimes necessary.

    First, if testing is done soon after an allergic reaction, it is possible that the food-specific antibodies have been used up and more have not had time to be replaced. Your allergist may wish to repeat the tests at a later date to see if this has happened.

    The testing extracts used for skin prick testing have been processed from the original foods, but sometimes this results in changes in the shape of the food molecules so they no longer fit into the lock of the allergic antibodies, and the test can be falsely negative.

    The blood tests use a different method to bind the allergens of the food in questions to a matrix that wily negative allow the detection of allergic antibodies in a sample of the patients blood, and sometimes the allergic antibodies can still recognize the allergens in this condition, but not always, so this test can be falsely negative too.

    And sometimes a patient will make allergic antibodies locally, only in the gastrointestinal tract, but not in sufficient quantities to spill over into the bloodstream or skin, so skin prick test, and blood tests are negative, but the patient does react with an oral challenge.

    You May Like: Can Seasonal Allergies Make You Throw Up

    Allergy Solutions Used In Allergy Tests

    The solutions to be used in allergy tests vary according to the type of allergy disease and the place where they live. Allergy test solutions used for allergy tests consist of a mixture of allergenic and non-allergenic components obtained from the allergen source. Therefore, crude extracts consist of original sensitizers and cross-reacting proteins. Generally, allergens are mainly proteins or glycoproteins, but carbohydrates or other low molecular weight chemicals can cause allergic sensitization when converted into complete antigens.

    Allergen extracts are usually obtained from natural sources through aqueous extraction. Their composition and biological properties can be affected by the quality and purity of the source material, extraction and processing methods, and storage conditions. Extras should not contain more than one allergenic source and should not contain interacting preservatives such as thiomersal.

    Read Also: What Allergy Medicine Is Stronger Than Zyrtec

    What Age Is Appropriate For Allergy Skin Testing

    Per the American Academy of Pediatrics, age is not a barrier to skin testing. Even infants can benefit. As the childs immune system develops, the child should be retested to identify changes in his/her immune response. Many times foods can be reintroduced into the diet that once caused an allergic reaction. In addition to Allergy & Immunology, our allergists train in either pediatrics or internal medicine, so we are very comfortable treating pediatric patients for allergies and asthma.

    Dont keep suffering from allergies. Schedule an appointment today with one of our board-certified allergists.

    Don’t Miss: Antibiotics Make Me Itchy

    Why Should You Submit Your Dog On Allergy Testing

    Allergy testing is a way to get a positive diagnosis for food allergies, contact allergies, or atopy allergies. Symptoms like scratching, licking the feet, chewing, and red, irritated skin are all clear signs of atopy in the dog or cat. Next to the flea bite, atopy is by far the most common cause of allergies in dogs.

    This is where quick home kits for dog allergy testing come in handy. When an allergy to a specific substance is identified, the dog can receive immunotherapy in the form of hyposensitisation injections.

    Does Allergy Testing Always Produce Accurate Results

    Allergist Dr. Linda Cox on Allergy Skin Testing

    Allergy testing is not 100% accurate in certain situations. There are times when a positive result can show even when you arent truly allergic. Its also possible to have a negative result when you really are allergic. Your allergist can combine allergy tests and track your symptoms to determine an accurate diagnosis.

    You May Like: Robitussin Medicine

    What Type Of Allergy Tests Are The Most Accurate And Why

    During your long-awaited camping vacation, you got stung by a bee and began swelling abnormally even though this has never happened before. Perhaps youve noticed that your kid keeps coughing and wheezing after relocating to your new home, and your chief suspect behind the bizarre reaction is dust. Allergies manifest themselves in various ways, and they can cause symptoms ranging from life-threatening to mild. If youve discovered or you are suspecting that you have an allergic reaction, you might want to make it clearer and know whats causing it. This way, you will know how to manage future allergic reactions and even learn how to prevent the allergens.

    Heres where allergy testing comes in. In this piece, we will discuss some of the most effective and accurate allergy tests that will help you answer your questions for once and for all.

    What Concerns Can Be Diagnosed

    Many common allergies can be diagnosed with a skin test, including respiratory allergies such as allergic rhinitis, or hay fever, and allergic asthma. The allergic irritation causing eczema can also be diagnosed with one of our tests. In addition, many food allergies, allergies to medications like penicillin, insect venom allergies, and latex allergies can be identified.

    The patch test is especially versatile in testing to allergies to common substances like dyes and preservatives. If you have questions about which allergies can be diagnosed, one of our doctors can answer them during an initial consultation.

    Recommended Reading: Compare Claritin Allegra Zyrtec

    Why Do Healthcare Providers Perform Allergy Tests

    Your healthcare provider may perform an allergy test if you have allergy symptoms that bother you. Providers also perform allergy tests on people who have asthma. The test can identify allergy triggers that can worsen asthma symptoms or bring on an asthma attack.

    You may also need a test if youve had a severe allergic reaction called anaphylaxis. This potentially life-threatening problem can cause hives or swelling, breathing difficulty and/or a sharp drop in blood pressure that brings on anaphylactic shock. Your health history along with allergy testing is used to determine the cause of severe reaction. If you have had an anaphylactic reaction or may be at risk for one, then you may need to carry an epinephrine auto-injector to treat the symptoms.

    Food Challenge And Elimination Testing

    Allergy Skin Prick Test Results

    In a few cases, your doctor may put you through the food challenge and elimination test. Here, you will be handled food that you suspect to be causing allergies. Your doctor will carefully increase the amounts of food to see how you react while closely monitoring your progress. Your doctor will eliminate food that doesnt seem to cause reactions. Although this test is riskier compared to the above-discussed allergy tests, it is the most accurate method used in diagnosing food allergies. The food challenge test is best carried out in a clinic where a doctor can attend to severe reactions if they develop.

    There you have it! Some of the most accurate allergy tests and everything you need to know about them. Do you suspect that you have some form of allergy? Erase your doubts by reaching us through our contact information to book an appointment with us today at .

    You May Like: Can Antihistamines Raise Blood Pressure


    Most Popular