Diagnosis of Allergies

If your symptoms become persistent and bothersome, visit your family physician or an allergist. They can test for allergy sensitivities by using a skin or blood test. The test results, along with a medical exam and information about when and where your symptoms occur, will help your doctor determine the cause.

Source: NIH News in Health (NIH)1

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Doctors use skin and blood tests to diagnose allergies.

Source: MedLinePlus (NIH)2

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Diagnosis

Testing for Allergies

Knowing exactly what you are allergic to can help you lessen or prevent exposure and treat your reactions. There are several tests to pinpoint allergies:

  • Allergy skin tests—Allergy skin testing provides rapid results within a few minutes. The most common test is the "prick test," which involves pricking the skin with the extract of a specific allergen, then observing the skin's reaction.
  • Serum-specific IgE antibody testing—These blood tests provide information similar to allergy skin testing.

Source: MedLinePlus Magazine (NIH)3

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Diagnosis

Testing for Allergies

Knowing exactly what you are allergic to can help you lessen or prevent exposure and treat your reactions. There are several tests to pinpoint allergies:

  • Allergy skin tests—Allergy skin testing is considered the most sensitive testing method and provides rapid results. The most common test is the "prick test," which involves pricking the skin with the extract of a specific allergen, then observing the skin's reaction.
  • Serum-specific IgE antibody testing—These blood tests provide information similar to allergy skin testing.

Source: MedLinePlus Magazine (NIH)4

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Your doctor will ask about your history of symptoms and examine you. To identify a food allergy your doctor may suggest that you avoid the food for a while, then try eating it again to see if your symptoms return.

Your doctor may do a skin scratch or prick test, which will check for reactions to tiny amounts of possible allergens placed under your skin. Blood tests can also help identify what you are allergic to.

Call Healthline 0800 611 116 if you are unsure what you should do.

Source: New Zealand Health5

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Diagnosis

Your GP will often be able to diagnose allergic rhinitis from your symptoms and your personal and family medical history.

They'll ask you whether you've noticed any triggers that seem to cause a reaction, and whether it happens at a particular place or time.

Your GP may examine the inside of your nose to check for nasal polyps.

Nasal polyps are fleshy swellings that grow from the lining of your nose or your sinuses, the small cavities inside your nose. They can be caused by the inflammation that occurs as a result of allergic rhinitis.

Allergic rhinitis is usually confirmed when medical treatment starts. If you respond well to antihistamines, it's almost certain that your symptoms are caused by an allergy.

Source: NHS Choices UK6

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Getting help for allergies

See your GP if you think you or your child might have had an allergic reaction to something.

The symptoms of an allergic reaction can also be caused by other conditions. Your GP can help determine whether it's likely you have an allergy.

If your GP thinks you might have a mild allergy, they can offer advice and treatment to help manage the condition.

If your allergy is particularly severe or it's not clear what you're allergic to, your GP may refer you to an allergy specialist for testing and advice about treatment.

Read more about allergy testing.

Source: NHS Choices UK7

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Diagnosis

If you think you have an allergy, tell your GP about the symptoms you're having, when they happen, how often they occur and if anything seems to trigger them.

Your GP can offer advice and treatment for mild allergies with a clear cause.

If your allergy is more severe or it's not obvious what you're allergic to, you may be referred for allergy testing at a specialist allergy clinic.

Skin prick testing

Skin prick testing is one of the most common allergy tests.

It involves putting a drop of liquid onto your forearm that contains a substance you may be allergic to. The skin under the drop is then gently pricked with a needle. If you are allergic to the substance, an itchy, red bump will appear within 15 minutes.

Skin prick testing is painless and very safe. Make sure you don't take antihistamines before the test, as they can interfere with the results.

Blood tests

Blood tests may be used instead of, or alongside, skin prick tests to help diagnose common allergies.

A sample of your blood is removed and analysed for specific antibodies produced by your immune system in response to an allergen.

Patch tests

Patch tests are used to investigate a type of eczema known as contact dermatitis, which can be caused by your skin being exposed to an allergen.

A small amount of the suspected allergen is added to special metal discs, which are then taped to your skin for 48 hours and monitored for a reaction.

Elimination diet

If you have a suspected food allergy, you may be advised to avoid eating a particular food to see if your symptoms improve.

After a few weeks, you may then be asked to eat the food again to check if you have another reaction.

Don't attempt to do this yourself without discussing it with a qualified healthcare professional.

Challenge testing

In a few cases, a test called a food challenge may also be used to diagnose a food allergy.

During the test, you're given the food you think you're allergic to in gradually increasing amounts, to see how you react under close supervision.

This test is riskier than other forms of testing, as it could cause a severe reaction, but is the most accurate way to diagnose food allergies. And challenge testing is always carried out in a clinic where a severe reaction can be treated if it does develop.

Allergy testing kits

The use of commercial allergy-testing kits isn't recommended. These tests are often of a lower standard than those provided by the NHS or accredited private clinics and are generally considered to be unreliable.

Allergy tests should be interpreted by a qualified professional who has detailed knowledge of your symptoms and medical history.

Source: NHS Choices UK8

Tests for Allergies

Allergy testing

If the exact cause of allergic rhinitis is uncertain, your GP may refer you to a hospital allergy clinic for allergy testing.

The two main allergy tests are:

  • skin prick test - where the allergen is placed on your arm and the surface of the skin is pricked with a needle to introduce the allergen to your immune system; if you're allergic to the substance, a small itchy spot (welt) will appear
  • blood test - to check for the immunoglobulin E (IgE) antibody in your blood; your immune system produces this antibody in response to a suspected allergen

Commercial allergy testing kits aren't recommended because the testing is often of a lower standard than that provided by the NHS or an accredited private clinic.

It's also important that the test results are interpreted by a qualified healthcare professional with detailed knowledge of your symptoms and medical history.

Source: NHS Choices UK9

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Further tests

In some cases further hospital tests may be needed to check for complications, such as nasal polyps or sinusitis.

For example, you may need:

  • a nasal endoscopy - where a thin tube with a light source and video camera at one end (endoscope) is inserted up your nose so your doctor can see inside your nose
  • a nasal inspiratory flow test - where a small device is placed over your mouth and nose to measure the air flow when you inhale through your nose
  • a computerised tomography (CT) scan - a scan that uses X-rays and a computer to create detailed images of the inside of the body

Source: NHS Choices UK10

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References

  1. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ issue/ jun2016/ feature2
  2. Source: MedLinePlus (NIH): medlineplus.gov/ allergy.html
  3. Source: MedLinePlus Magazine (NIH): medlineplus.gov/ magazine/ issues/ spring15/ articles/ spring15pg26-27.html
  4. Source: MedLinePlus Magazine (NIH): medlineplus.gov/ magazine/ issues/ spring13/ articles/ spring13pg24.html
  5. Source: New Zealand Health: health.govt.nz/ your-health/ conditions-and-treatments/ diseases-and-illnesses/ allergies
  6. Source: NHS Choices UK: nhs.uk/ conditions/ allergic-rhinitis/ diagnosis/ 
  7. Source: NHS Choices UK: nhs.uk/ conditions/ Allergies/ 
  8. Source: NHS Choices UK: nhs.uk/ conditions/ allergies/ diagnosis/ 
  9. Source: NHS Choices UK: nhs.uk/ conditions/ allergic-rhinitis/ diagnosis/ 
  10. ibid.

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.