Allergy Testing

Allergy Testing

Allergies are quite common these days and the problem is on the rise. The number of individuals with allergies has increased in India. It is believed that this is due to genetic components, pollution, and improved hygiene.

Allergy testing is a procedure during which your skin is exposed to suspected allergy-causing agents and it is monitored for signs of an allergic reaction. Apart from your medical history, allergy tests might help to confirm whether a particular substance you breathe, touch, or eat is giving rise to symptoms.

The information derived from allergy testing helps your healthcare provider formulate an allergy treatment plan that includes medications, allergen avoidance, and immunotherapy or allergy shots.

Allergy skin tests are being diversely used to help detect allergic conditions like allergic asthma, hay fever, food allergies, dermatitis, bee venom allergy, and penicillin allergy. Generally, skin tests are safe for children and adults of all ages. However, in some cases, skin tests are not recommended. Your healthcare provider may advise against skin testing if you:

  • Take medications that could interfere with the test results. These include some antidepressants, antihistamine, and certain heartburn medications. Your healthcare provider may determine if it is safe for you to continue taking these medications or to temporarily cease taking those in preparation for a skin test.
  • Have ever developed a severe allergic reaction: Your body may be so sensitive to certain agents that even little amounts of those that are used in skin tests could give rise to a life-threatening reaction known as anaphylaxis.
  • Have certain skin conditions: If psoriasis or severe eczema involves large skin areas on your arms and back, which are the usual sites for testing, an adequate amount of clear, uninvolved skin may not be available to perform a test effectively. Other skin conditions like dermatographism can also give rise to unreliable test results. Blood tests are useful for individuals who are not fit for skin tests. These tests are not used for testing for penicillin allergy.

Generally, allergy skin tests can be relied on for diagnosing allergies to airborne agents like pet dander, pollen, and dust mites. Skin testing may help detect food allergies. However, as food allergies can be complicated, you may require additional tests or procedures.

Allergens are agents that can give rise to an allergic reaction. Those are primarily of three types:

  • Inhaled allergens
    These are the allergens that affect the body when they come in contact with the membranes of the lungs or the throat or nostrils. The most common inhaled allergen is pollen.
  • Ingested allergens
    These are the allergens that are present in some foods like soy, peanuts, and seafood.
  • Contact allergens
    These allergens produce an allergic reaction when they come in contact with the skin. Rash and itching caused by poison ivy is an example of a reaction from contact dermatitis. During allergy tests, you are exposed to a tiny amount of a particular allergen and then your reaction to it is recorded.

When your immune system reacts abnormally to a common agent in the environment, an allergic response occurs. That agent or substance is called allergen. It gives rise to an inflammatory response in the body, ranging from mild to life-threatening.

Slightly swollen, itchy, red bumps are the most common side effect of skin testing. These lesions are noticeable mostly only during the test. However, in some people, an area of redness, swelling, and itching may develop after a few hours of the test and remain for a couple of days.

Very rarely, allergy skin tests can give rise to a severe, immediate allergic reaction. Therefore, it is important to undergo skin tests at a hospital where adequate emergency medications and equipment are available.

Before a skin test is recommended, your doctor will ask you detailed questions regarding your signs and symptoms, medical history, and your usual way of dealing with your symptoms. Your answers can help him find out if allergies run in your family and if your symptoms are most likely occurring as a result of an allergic reaction. Your doctor may also perform a physical examination so that additional clues regarding the cause of your signs and symptoms may be searched.

Medications can interfere with results

Before you schedule a skin test, bring a list of all your over-the-counter and prescription medications to your doctor. Allergic reactions can be suppressed by some medications, which prevent the skin testing from producing accurate results. Other medications may enhance your risk of developing a life-threatening allergic response during the test.

As medications are cleared out of the body at varying rates, your healthcare provider may suggest you stop taking certain medications for around ten days. There are also some medications that may interfere with your skin tests. You may be asked to stop those before the test.

Before skin testing, a nurse usually administers the test, and another healthcare provider interprets the results. This typically takes around 20-40 minutes. Some tests diagnose immediate allergic reactions, which develop within minutes of exposure to a possible allergen. Other tests can detect delayed allergic reactions, developing over a period of several days.

Skin prick test

A skin prick test or a scratch test or puncture test is used to detect immediate allergic reactions to more than 50 potential allergic agents at once. This test is usually performed to identify allergies to mould, pollen, pet dander, foods, and dust mites. The test is usually performed on the forearm in adults. For children, the test may be performed on the upper back.

Allergy skin tests are generally not painful as it involves lancets and needles that barely penetrate the surface of the skin. You won’t feel more than mild discomfort or bleeding while undergoing these tests.

After disinfecting the area with alcohol, the nurse draws tiny marks on the skin and puts a drop of allergen extract next to each mark. Then, they use a lancet to prick the extracts into the surface of the skin. For each allergen, a new lancet is used.

To check if your skin is reacting normally, two more agents are scratched into the surface of the skin:

  • Histamine
    This substance triggers a skin response in most individuals. If you don’t react to it, it means that the allergy skin test may not reveal an allergy even if you have one.
  • Glycerin or saline
    These substances don’t cause a reaction in most people. If you do react to these, it means that your skin is sensitive. To avoid false allergy diagnosis, test results will need to be interpreted cautiously. Around 15 minutes after the skin pricks, your skin is observed for signs of allergic reactions. If you are allergic to one of the agents tested, you will develop a red, raised, itchy bump that may appear like a mosquito bite. The healthcare provider will then measure the size of the bump and record the results. Then, they will sterilise your skin with alcohol so that the marks are removed.

Skin injection test

You might require a test that involves injecting a small amount of allergen extract just into the skin of the arm with the help of a needle. After around 15 minutes, the injection site is examined for signs of an allergic reaction. Your healthcare provider may recommend you to undergo this test to check for allergies against penicillin or venom.

Patch test

Patch testing is usually performed to detect whether a particular substance is triggering allergic skin reaction or inflammation. Patch tests can be used to detect delayed reactions, which can take several days to develop. These tests don’t involve the use of needles. Instead, allergies are put on patches, which are then applied to the skin. Your skin may be exposed to 20 to 30 extracts of different contact dermatitis causing substances during a patch test. These can include medications, latex, fumes, preservatives, fragrances, metals, hair dyed, and resins.

You will be asked to wear the patches on your back or arm for 48 hours. During this time, you should avoid performing activities causing heavy sweating. When you return to the hospital, the patches are removed. Irritated skin at the site where the patch was applied indicates an allergy.

Before you leave the hospital, you will be informed about the results of an intradermal test or skin prick test. A patch test may take several days for the results to be produced.

If you have a positive skin test, it means that you may be allergic to a particular substance. Larger wheals usually indicate a higher degree of sensitivity. A negative skin test indicates that you probably are not allergic to a particular allergen.

You must remember that skin tests aren’t accurate. Sometimes, they indicate an allergy when there is not one. Skin testing may also trigger a reaction when you are exposed to something you are not allergic to. You may react differently even if you undergo the same test performed at different occasions.

The treatment plan for your allergy may include immunotherapy, medications, changes to your home or work environment, or dietary changes. Ask your healthcare provider to explain anything about your treatment or diagnosis if you don’t understand it. With test results that diagnose your allergy and a suitable treatment plan that helps you take control, you will be able to decrease or eliminate the signs and symptoms of allergy.

The Department of Pulmonary Medicine at Kokilaben Dhirubhai Ambani Hospital, Indore, offers comprehensive diagnostic and therapeutic care for a diverse range of pulmonological diseases. Our services include endoscopic ultrasound, endo bronchial ultrasound, endobronchial brachytherapy, innovative therapeutic techniques, bronchial thermoplasty and surgical interventions like video-assisted thoracoscopic surgery and lung volume reduction. Visit our team for the best allergy testing in Indore.