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Using Blood Tests to Diagnose Hay Fever

By: Ian Murnaghan BSc (hons), MSc - Updated: 26 Dec 2012 | comments*Discuss
Blood Tests Diagnosing Hay Fever Timely

Accurately diagnosing hay fever is crucial to obtaining timely and effective treatment for your symptoms. Your doctor will examine you and take a thorough history to determine how and when your hay fever symptoms occur as well as determine any familial history of allergies. He or she may then order blood testing to provide further information regarding the cause of your symptoms.

One test that your doctor may order is a blood test that looks at a blood protein known as IgE. This protein is found in people who have allergies such as hay fever. The IgE test is also known as the radioallergosorbent test (RAST); it will check for elevated levels of the IgE antibody which can help your doctor to decide if hay fever is the cause of your symptoms.

How The Test Works

A blood sample will be taken and then tested for the IgE antibody in relation to a specific allergen. For example, if a person showed a high level of IgE against pollen, this would possibly indicate the person is allergic to pollen. Although the RAST is somewhat more invasive than other forms of testing, its results are considered useful for providing diagnosis of hay fever.


An important feature of this test is its use in people who have skin conditions that may affect the accuracy and use of a skin test. Also, if a patient has an extremely high sensitivity to an allergen, a RAST is considered superior to a skin test with regards to safety and prevention of serious side effects from administering the test.

Another benefit is that it can detect the specific allergens causing your allergy distress so that you can make lifestyle changes with reference to those allergens that trigger your symptoms, rather than all hay fever triggers that exist.


The RAST can take a week or more to provide results and unfortunately, it can also provide a false positive result. It is also thought to be less sensitive than a skin prick test and can't pick up as many allergic substances at once in comparison with the skin prick test. Your doctor likely won't, however, solely rely on this test for diagnosis and instead, will use the results as one tool to provide an accurate hay fever diagnosis.

Allergy Specialists

Most likely, your doctor will be able to make a diagnosis from a combination of blood testing, examination or other forms of diagnostic testing. If your doctor still feels further investigations are necessary, he or she may refer you to an allergy specialist. An allergy specialist will be able to help you pinpoint your allergy causes as well as develop a preventative treatment plan.

Blood tests are a standard means to assessing allergies but are only one tool in a pool of many that your doctor may order to properly diagnose hay fever. The RAST can help to pinpoint if you are suffering from hay fever and can help you to find which specific allergens are causing your hay fever symptoms.

Once your doctor has identified those allergens that trigger your symptoms, you can work together to find a prevention and treatment plan that lets you live hay fever free, despite the allergens that will continue to exist.

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