Skin prick testing is a test used to help diagnose allergies. In regards to asthma, skin prick testing may be useful to identify potential allergy triggers, such as house dust mites, pet dander, or food.

The test is reliable and painless, involving small drops of the “allergen" being placed onto the forearm or back, then the skin is pricked to allow a tiny amount of the allergen into the skin. Reactions are then measured and reported to, or observed by, the doctor.

Although the test may indicate a suspected allergy, the person's clinical history is crucial in confirming a diagnosis. It is important that the results are interpreted by an experienced doctor or allergy specialist, and coupled with other test results and your actual allergy and reaction history. For example, negative skin prick tests may indicate a different type of response, and positive tests do not necessarily mean that you are allergic to that food, or that that particular allergen is the sole reason for your asthma.

In the case of food allergy, an immediate-type allergic response when a specific food is eaten, or a severe reaction such as anaphylaxis on first time a particular food is introduced to a young child, a diagnosis of allergy to that food may not need a test to confirm. Where it is not as clear, your doctor may advise you to keep a food and symptom diary. Over a period of a week or two, a pattern may emerge. However, it is important to note that if reactions to a particular food are obvious, the food in question should be avoided until you have consulted your doctor. In the case of a child, they may then be referred to a specialist.

A blood test called RAST or EAST can also be used to help with diagnosing allergies, and may be preferred where someone is not be able to have a skin prick test because other medications they are taking, such as anti-histamines, could interfere with the results.

If you have questions about skin prick testing, talk to your GP or the helpful team at Allergy NZ.