Skin prick testing

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How does skin prick testing work?

Skin prick testing is used to investigate conditions such as hayfever or food allergy. It involves putting small amounts of allergen solutions onto the skin of your arm then pricking through the drop with a lancet. This allows a small amount of allergen into the skin. If you are sensitised’ to that allergen, a small itchy ‘wheal’ appears after a few minutes.

Allergy tests can be very tricky to interpret. Positive test results aren’t always important, and sometimes negative tests don’t exclude allergy completely. It’s very important to relate the skin tests to your symptoms and sometimes further tests are needed.

How do I prepare for testing?

How is this test done?

These reactions can include:
• The nurse will put numbered tape on your forearm. This will be used to keep track of the different allergens.
• A small drop of each allergen will be placed on your skin. We will also apply a drop of histamine. This should cause a reaction and shows us that the test has worked properly.
• The nurse will lightly prick the surface of your skin under each drop so a small amount of the allergen will seep into the skin. The procedure isn’t usually painful but some people find it slightly irritating.
• The test is read at around 15 minutes. We’re looking for a red, itchy bump to show a positive result. The area where the allergen was placed will look like a mosquito bite surrounded by a red ring.
• After the test we’ll discuss the results and further plans with you. Sometimes if the results don’t give us a complete answer we might organise blood tests afterwards.

Are there any risks?

There is no risk of severe allergic reaction during this procedure. The only side effect is an itchy arm. The itchy bumps usually settle down within a few hours. Occasionally very strong positive results last for longer.

Where is the test performed?

You will be given an appointment to attend the Royal Sussex County Hospital, Outpatient Department in Eastern Road, Brighton. Please try to arrive as near to your appointment time as possible, as seating in the waiting area is limited. You may be asked to wear a mask.

Who can I contact for further information and advice?