Helpline
Blood testing
What is an allergy blood test?
This is a very specific blood test for allergy, not usually part of a just a routine blood testing. After an allergy clinical history is taken. Suspected allergens are selected for testing and the blood test will measure those specific allergens only. This is called Specific IgE and can be test requested to various allergens such as peanut, house dust mite, grass pollen and others, depending on what the clinical history points to. There are so many different allergens that could be potentially tested for but this is not necessary, if a good clinical history. Only a select few need to be tested to help confirm if that specific allergen is driving allergy symptoms.
How is it done?
A small amount of blood is taken using a needle and syringe, in the usual way a blood test is done. The results need to be reviewed by a doctor who understands how to interpret these test results ie who has some expertise in allergy. You don’t need to stop taking antihistamines for this test, which is helpful for those who take them regularly.
Where can you get a Specific IgE blood test?
If your GP doesn’t specialise in allergies, they may refer you to a specialist.
Skin prick testing
What is a skin prick test?
A skin prick test is a common way to check for allergies and can be done for most allergens. Skin prick testing can be carried out on infants, children and adults. However, caution should be taken to interpret the tests in infancy as the accuracy may be reduced on children under two years old and so needs to be carried out by a paediatric allergy specialist.
How is it done?
A small drop of the allergen in a solution (like grass pollen, peanut or egg) is placed on the skin, and then a tiny prick is made to see if you have an itchy bump (wheal) which is then measured. If you’re on antihistamines, you will need to stop taking them a few days before the test. The test can check for multiple allergies at once, and a specialist should review the results with you.
Where can you get a skin prick test?
This test is done at a hospital or clinic, and results can be seen in about 15 minutes. It is usually a test that is done in an allergy service (although some community allergy clinics may do this), so you would need a referral from your GP. It is not a test that you can just walk into a hospital to get on the day like you can for routine blood tests.
Oral Food Challenge
What is an Oral Food Challenge?
An oral food challenge is considered the ‘gold standard’ test for diagnosing food allergy and is often offered when other allergy tests have not been clear or to see if a food allergy has been outgrown. They can also be used to confirm a food allergy following a positive allergy test where the person has never eaten that food.
How is it done?
At the start of the oral food challenge, you are given a very small and measured amount of the food. Once this first dose has been given you/your child will be closely observed for signs of an allergic reaction, for example a rash or swelling. It is very important that you tell them if you are experiencing any symptoms that they may not be able to see, for example itching or tingling. In oral food challenges for infants and children, they will always be fed and encouraged in an age-appropriate way.
The amount of time you spend at an oral food challenge appointment depends on many factors, including the schedule for the food with which you are being challenged and the staff and resources available. You can be at the setting for the oral food challenge for several hours.
Where can you undertake an Oral Food Challenge?
Oral food challenges are carried out in a safe environment, such as a hospital or allergy clinic, and under the supervision of allergy nurses or doctors who have the expertise to recognise and respond to an allergic reaction.
Component resolved diagnostics (CRD)
What is a CRD?
This blood test looks at a specific protein found in a single allergen that can help improve the diagnosis and risk assess for ongoing management. It is usually done for food allergies but can also be used for venom (Bee/Wasp) and pollen allergies.
These tests break down the allergens into their component proteins to see which parts may be causing the most concern. They can also provide additional information to determine the level of risk.
How is it done?
A blood test is taken in the usual way, but the sample is sent to a specialist laboratory which does this test, so these are not tests where you get results quickly. The interpretation of the results needs to be undertaken by someone experienced and qualified to provide specialist advice on allergy.
Are CRD tests easily accessible?
These tests are not required for most people and may be offered at specialised allergy services, so you need to have been referred to access this test as they are usually not available via GP services.
Patch Tests
What is a patch test?
This is a diagnostic test, which aims to find out if your skin condition is caused or worsened by something your skin may have come in contact with such as allergens and irritants. This type of test looks for hypersensitivity reactions of a delayed type, so is NOT suitable for testing food allergy or immediate reactions (IgE) such as from wasp/bee stings, pollen allergy etc
How is it done?
Usually set panels containing the most common substances causing skin reactions are applied to the body on the back/shoulder blades, these often include, cosmetics, preservatives, metals etc and can be tailored to some of your own personal toiletries or things you may come into contact within your home or workplace. They are applied as ‘patches’
Where can you get a patch test?
Patch testing is usually carried out in Dermatology services and some allergy services, so you usually require a referral to access these tests.
Home Testing Kits
There are many different types of tests that are available but not validated by science or recommended by allergists. These include vega testing, hair analysis and blood tests that don’t look for IgE.
Many of these tests are available to buy online and may seem a good idea due to the ease with which they can be bought. However, these are NOT recommended, as they may give false readings and may not be as accurate as those that have the scientific backing such as the ones outlined in the above section on allergy tests.
