Skin Prick Tests
Skin Prick Tests are used to help identify the allergen(s) implicated in IgE mediated allergies. These allergens cause the symptoms of allergy conditions such as hay fever/rhinitis, asthma, conjunctivitis, gastrointestinal disturbance and anaphylaxis. Skin Prick test results are interpreted alongside a comprehensive clinical history of the patient.
The diagnosis of the allergens responsible for these allergic responses is important in order to eliminate or minimise exposure wherever possible, decide whether an adrenalin pen should be carried and also to evaluate whether immunotherapy (desensitisation) may be appropriate.
The most common allergens that are most usually implicated in IgE-mediated allergy are:
- Inhaled allergens such as grass/weed/tree pollens, mould spores, house dust mites, cat & dog & horse epithelia
- Injected allergens such as bee venom and drugs
- Occupational allergens such as latex
- Ingested allergens such as various foods.
The skin prick test is usually done on the underside of the forearm however sometimes other areas may be used.
The arm will be marked with a pen to identify where the different allergens are placed. A small drop of each allergen being tested will be placed beside the corresponding mark on the arm. The allergen will then be exposed to the patient’s immune system just below the skin surface by a tiny lancet being used to prick the skin.
After 15 minutes, any reaction that develops will be measured and compared to the controls. A positive reaction is a small raised swelling or weal with a red edge.
A positive control (histamine) is always used to simulate an allergic type reaction and a negative test solution is also used. These controls are used to make sure the test panel has worked properly in every individual and is also used to assist in interpretation.
There is a small risk of a serious reaction occurring after the test. Because of this patients may be required to remain at the test location to be observed for up to 20 minutes after the test has been completed.
Skin Prick Tests are performed by trained health care professionals in allergy clinics, some doctors rooms and medical laboratories. Some tests such as penicillin/amoxycillin allergy testing are only carried out in highly specialised settings such as hospitals.
Skin Prick Tests are supplied pursuant to s29 of the Medicines Act 1981.