What is Skin Allergy Prick Test?
The skin prick test is a common method of determining whether you are sensitive to various allergens. It can also determine your degree of sensitivity to the allergen concerned. The skin prick test is easy and the results are immediate.
The method involves introducing small quantities of different allergens to your skin (usually on your arm) and see if it causes swelling. The degree of swelling indicates an allergy to the substance and gives an indication of the degree of sensitivity to the substance.
How useful is skin test prick?
Skin prick testing is most often used to demonstrate atopy. Atopy is characterised by an overactive immune response to environmental factors and has a strong genetic component. It usually manifests clinically as one or more of the characteristic disorders of eczema, asthma, or allergic rhinitis (sensitive nose). The results from skin prick tests can be used to guide the management of patients e.g. desensitization to a certain allergen, removal of a family pet, removal of carpets, avoidance of certain foods.
Other conditions that may benefit from skin prick testing include acute urticaria (hives) and angiodema, and insect stings, especially if immunotherapy is being considered.
PRICK TEST PROCEDURE
Your co-operation is needed to ensure the successful outcome of the test. Please observe the following points:
- 3 days before the test, you must not take any antihistamines (medicine for flu and cold) as these will bias the results.
- The test is usually done on the inner forearm.
- A specialised sterile plastic device is dipped intothe various allergens and then used to lightly scratch your skin. There is no bleeding or scarring. Once used, the disposable device is discarded.
- The test area will be marked to prevent confusion among the allergens used. Within 20 minutes, your nurse will assess your reaction and grade it on a scale of 0 to 4.
- In addition to the allergens tested, there should be a positive and negative control. The positive control, usually a histamine solution, should become itchy within a few minutes and then become red and swollen with a “wheal” in the centre. The negative control, usually a saline solution should show no response.
What comes next?
Your dermatologist will explain the significance of your skin prick test results and its relevance in the management of your skin rash problem.