Everything you Need to Know About Allergies (part 3): Diagnosis of Allergies

When you break out in hives after taking penicillin drugs or start sneezing every time you pet a dog, you already know the allergen that is causing it. But many a time, the cause of your allergic reaction is unknown. That is when the diagnosis of allergies is needed to prevent the occurrence.

Diagnosing an allergy is typically performed by first analyzing your medical history and performing a physical examination. The allergist will want to track any symptoms that have occurred in the past related to the allergy. Your doctor may also do a physical check-up to verify your symptoms. This is followed by allergy tests that firmly point out the cause.

History Taking

Your doctor will want to know everything you were exposed to before your allergy started. This gives them a complete understanding of the symptoms and a possible cause. They will carefully review the person’s symptoms, family history, personal history that includes the age of onset and seasonal symptoms, and/or environmental symptoms.

You will be asked about your family history, foods that you take, lifestyle, places, and things that you are exposed to. They will also ask you detailed questions about the history of allergy symptoms, the time length that it took for the symptoms to develop and how long they lasted.

Based on the information given, your doctor will recommend further tests.

Allergy tests are carried out by trained specialists. The tests that are carried out are

  • Skin tests
  • Blood tests and
  • Elimination diet

Skin Tests for Diagnosis of Allergies

Skin tests are usually done to identify allergens that may include contact allergens, inhaled allergens, and ingested allergens. The three types of skin tests that are usually conducted are:

  • Scratch test: In this test, the allergen is placed in liquid and the liquid then placed on a section of your skin with a special tool that lightly punctures the allergen into the skin’s surface. You are then kept under observation and closely monitored for any allergic reaction on the test site. If you are allergic to that particular allergen, you show some form of reaction. 
  • Intradermal test: Incase the scratch test doesn’t give any conclusive results, you may have to do an intradermal skin test. In this test, a tiny amount of allergen is injected into the dermis layer of your skin. Again you are monitored for any reactions and diagnosed accordingly.
  • Patch test: T.R.U.E test (Thin-layer Rapid Use Epicutaneous Patch Test) is another form of skin test. This involves an epicutaneous patch test that helps in the diagnosis of allergy. Three adhesive panels of allergens and allergen mixes are stuck to your back. Each panel has 12 patches of possible allergens that you wear for 2 days. The patches are then reviewed. It is taken off to see whether there has been any reaction. Some reactions occur late so you may have to go back later after 72 to 96 hours.
  • In case there is a mild reaction in any patch test, you probably have to follow it up with a R.O.A.T test (Repeat Open Application Test). This test can be done yourself. You will be asked to apply the suspected allergen on your skin during the day for several consecutive days. It will be then reviewed.

Blood Tests

Skin tests are the most common allergic tests for allergen detection. In case you show a severe allergic reaction to any of the skin tests, blood tests are done. Lab blood tests are done to check for the presence of antibodies that fight specific allergens. This test is also known as the ImmunoCAP allergy test and has been noted to be successful in detecting IgE antibodies to major allergens.

Allergy lab tests include Allergy blood testing, total IgE, histamine, tryptase, complete blood count (CBC), and White blood cell (WBC) Differential test that has been described in detail earlier. These are all examples of allergy blood testing.

  • Serum total IgE testing: The total IgE in the blood is measured. However, this test isn’t very helpful sometimes as conditions such as parasitic infections, bacteria or virus infections, malignancies, and fungi can also increase the total IgE. Not always serum total IgE means that a patient is allergic. Therefore, specific IgE tests are more effective.
  • Allergen Specific IgE testing: This blood analysis entails the measurement of specific IgE which is directed against a specific allergen. Blood is taken and sent to the laboratory. The lab adds the suspected allergen in your blood sample and then measures the number of antibodies your blood produces as a reaction. Higher is the level of specific IgE, the more intense is the allergy symptom. Specific IgE is also popularly known as the RAST test or Radioallergosorbent test, CAP, ELISA, etc.

RAST was the traditional method of blood testing but now has been largely replaced with newer IgE-specific immunoassay methods. Phadiatop allergy test is a commercially available qualitative serological test that is used for screening allergic sensitization in patients with suspected allergic diseases. It is designed to detect allergen-specific IgE antibodies to food and inhalant allergens.

  • Complete blood count (CBC) and WBC differential which involves the measurement of eosinophils. The levels of eosinophils may be higher in people with allergies.
  • Histamine and Tryptase blood test that is helpful in diagnosing anaphylaxis or activation of the mast cell.

Food Allergies Test

Food allergy tests can be extremely complicated. They can affect your skin, respiratory tract, gastrointestinal tract, and even cardiovascular system. It can develop at any age at any time.

The allergist usually will order a blood test such as an ImmunoCAP test or perform a skin prick test to determine food-specific IgE antibodies in your blood.

Elimination Diet

An elimination diet is mainly done to detect food allergies. It entitles the elimination of certain allergy-causing food and observing your body’s reaction. It is then slowly incorporated into your diet one by one. Each time you reintroduce a food, you are checked for symptoms of an allergic reaction. Elimination diets are helpful in pinpointing specific food that might be causing the allergy. 

  • Lactose allergy test: Lactose allergy is actually a case of lactose intolerance which is caused by the deficiency of the enzyme lactase. A hydrogen breath test, stool acidity test, and lactose intolerance test can help diagnose it. 

However, milk allergies are quite prevalent and can cause mild to severe symptoms. You can be allergic to milk proteins such as casein and whey. Both casein allergy tests and whey allergy tests are allergen-specific IgE blood tests that determine casein and whey allergy.

  • Tomato allergy test: A tomato allergy is a Type I hypersensitivity to tomatoes. Tomato or tomato-based products cause the release of histamines in exposed areas such as skin, nose, respiratory and digestive tract causing an allergic reaction.
  • Cinnamon allergy test: Around 2 percent of allergies are related to spice allergy. Ingestion or direct contact with cinnamon can trigger allergic reactions such as trouble breathing, wheezing, itching of body parts, nasal congestion, and swelling of body parts. Anaphylaxis to cinnamon allergy is rare but has been reported. Multiple tests are needed for the diagnosis of cinnamon allergy. A blood test and a skin patch test usually can diagnose the allergy.

Oral Food Challenges (OFC)

Sometimes skin prick and blood tests can’t give a definite diagnosis. This is mainly in case of food allergies. Under the circumstances, a highly accurate diagnostic test is suggested which is the Oral Food Challenge. The allergist feeds you the suspected allergen in measured doses and keeps you under observation. They normally start with a very little dose and gradually increase the amount.

There are three kinds of oral food challenges. They are:

  • Double-Blind Placebo-Controlled Food Challenge (DBPCFC)
  • Single-Blind Food Challenge
  • Open-Food Challenge

Environmental Allergy Tests

Environmental allergies can occur and by physical contact with the allergen or by inhaling the allergen. The diagnostic test for environmental allergy is skin test and blood test.

The environmental allergy blood test measures the amount of immunoglobulin (IgE) antibodies that are allergen-specific.

  • Seasonal allergy testing includes medical history taking and then goes for skin or blood testing.
  • Metal allergy testing: Metal allergy mostly results in contact dermatitis. Epicutaneous patch testing is usually done to diagnose metal allergy. Oral metal challenges are sometimes performed to diagnose metal allergy especially systemic contact dermatitis (1).
  • Chemical allergen test is mostly a patch test that involves common allergens that include balsam of Peru, fragrance mix, carba mix, ammonium persulfate (APS), preservatives, PPD, and minoxidil.
  • Polyester allergy test: Allergy to polyester is very well an example of fabric allergy and is often referred to as textile dermatitis. It is a contact allergy that is shown predominantly on the skin. An allergy patch test can identify the allergen.
  • Latex allergy diagnosis: the first step in the diagnosis of latex allergy is taking the clinical history of the patient followed by in vitro immunological testing in case the history supports an IgE mediated reaction.

Drug Allergy Tests

Drug allergies can be overdiagnosed or misdiagnosed. Therefore a detailed test is needed to confirm the specific allergen. It usually starts with a history taking followed by skin tests and blood tests.

Usually, a drug allergy test is of three types:

  • Skin test
  • A patch test is done to check for reactions to antibiotics or anticonvulsants
  • Blood test 

Allergy Tests for Different Body Locations

  • Throat allergy test: Throat allergy can be part of an Oral Allergy Syndrome (OAS) which can be severe throat swelling leading to difficulties in breathing and swallowing. Although there is no definitive test for OAS, the affected person is often suggested to have an allergy skin test or blood test for a specific protein, and history is taken (2).
  • Urticaria allergy test: The diagnosis of acute urticaria is history taking to uncover the possible trigger factor such as medications, infections, or foods. In case of very strong symptoms skin prick testing, and measurement of specific IgE is conducted (3).
  • Sinus allergy test: The test that is conducted for detecting sinus allergy is an allergy skin test.
  • Lung allergy test: Lung function tests such as spirometry, challenge tests, peak flow meter tests, and exhaled nitric oxide tests are the ones that are conducted for the diagnosis of lung allergy. 
  • Eye allergy test: Eye allergies have some symptoms common to diseases related to the eyes. Therefore it is imperative to diagnose an eye allergy and start the right treatment. It involves an examination of the eye with a microscope to see the swollen blood vessels on the surface of the eye (4).

Test for a certain type of white blood cell that shows up on the affected area of the eye by gently scraping the conjunctiva and diagnosing.

  • Nose allergy test: Skin prick testing is often done to diagnose nasal allergies. In this nasal allergy test, a very small amount of suspected allergen is ingested within the skin and checked for any reaction. Blood tests are also conducted sometimes to look for a specific antibody that can name the allergen.

Allergic Rhinitis Test

First, a comprehensive history and physical examination is done to detect the cause of allergic rhinitis. It can also help detect the allergen causing cold and sneezing allergies (5).

If that is not enough, allergy blood tests are suggested.

Diagnostic test for allergic rhinitis: The percutaneous skin test and the allergen-specific immunoglobulin E (IgE) antibody test are the most common diagnostic tests for allergic rhinitis (6).

Amongst the less common diagnostic tests, we have nasal provocation testing, nasal cytology, nasolaryngoscopy, and intradermal skin testing.

The differential diagnosis for allergic rhinitis: The differential diagnosis for allergic rhinitis is extensive. This is important to understand whether it is infective rhinitis or irritant rhinitis. For infective rhinitis, a short history of approximately one week is taken including the symptoms of upper respiratory tract infection. When the symptoms follow known physical or chemical irritants, it is confirmed to be the case of irritant rhinitis.

  • Allergy breathing test: The breathing test is a non-invasive procedure that doesn’t entail needles or blood taken. Also known as complete pulmonary function tests it basically is used to diagnose asthma. It includes spirometry, exhaled nitric oxide, and challenge tests similar to the lung allergy test.
  • hs-CRP test: The high reactivity C-reactive protein (hs-CRP) test is a blood test that finds lower levels of C-reactive protein (CRP). This protein gives you the measure of general levels of inflammation. It is used to measure certain cases of urticaria.

Insect Allergy Testing

The severity of an insect sting reaction varies from person to person and also depends upon the kind of insect sting. Wasps, honey bees, hornets, yellow jackets, and fire ants are to name a view. Some of them can be stung repeatedly as well.

To diagnose correctly, your doctor will ask you a detailed medical history about the sting and/or previous sting and symptoms experienced. He can also ask you to perform tests to diagnose insect allergies such as a skin prick test, intradermal test, or blood test.

Hormone Analysis – cortisol

To diagnose hormone deficiency as the cause of allergy, a hormone analysis test is done.

Cortisol is produced by the adrenal glands and it plays a crucial role in controlling the body’s histamine levels. Histamine is the chemical that acts as a mediator governing inflammatory responses in the body from allergies.

Cortisol production is a key factor in controlling the body’s histamine levels. Therefore, when the cortisol levels are suboptimal or deficient, allergy symptoms tend to be more severe. Therefore, a hormone analysis of cortisol can give a fair idea of allergy in the body.

Nambudripad’s Allergy Elimination Techniques (NAET)

This technique is a form of alternative medicine that has been claimed to identify and treat allergies. A California-based chiropractor and acupuncturist, Devi Nambudripad, devised this technique in 1983 (7).

It was a combination of ideas applied from different fields and methods. They were applied kinesiology, acupuncture, acupressure, nutritional management, and chiropractic methods.

In contrast to the conventional western understanding of allergies, Nambudsripad stated that allergy was a condition caused by repulsive electromagnetic fields between an individual and the object that he is allergic to (allergen).

According to him, the cumulative effects of these energy disturbances give rise to health disorders. He also added that 95 percent of all health ailments were a result of some of the other allergies. And he theorized that these allergies could be eliminated through the use of acupuncture or acupressure.

NAET practitioners use a form of applied kinesiology (which is the use of muscle testing to identify imbalances in the body’s structural, chemical, and emotional energy), called Neuromuscular Sensitivity Testing (NST or NST- NAET) to diagnose allergies. They then aim to remove energy blockages.