The optimal management of allergic disease requires the accurate diagnosis of a patient’s allergic sensitivities. Allergy testing has been shown to increase the accuracy of diagnosis when interpreted alongside a comprehensive history and clinical examination. Allergy testing is important to differentiate allergic diseases from other mimicking conditions, and enable better allergen avoidance strategies, improved use of medications, and for some patients, desensitisation treatment (allergen immunotherapy).
Skin prick testing (SPT) is a major diagnostic tool in the field of allergy. SPT is recommended as a primary method for the identification of allergic sensitivities in such conditions as allergic rhinitis, conjunctivitis and asthma, atopic dermatitis, and food related acute urticaria, eczema and anaphylaxis (ASCIA, 2013).
SPT is not routinely indicated in the investigation of nonspecific rashes, chronic urticaria, food intolerance and chronic fatigue, in the absence of allergic features. Nor is it routinely indicated in the investigation of migraines, headaches, behavioural disorders and reactions to respiratory irritants (e.g. smoke, fumes, perfumes), assessment of allergen immunotherapy effectiveness, or to screen for allergy in the absence of symptoms (ASCIA, 2013).
SPT involves the introduction of small amounts of suspected allergens onto and just below the surface of the skin. A small, superficial break in the skin is made with prickers which have been dipped in allergen extracts. The skin is then closely observed for 15 minutes for signs of a wheal and flare reaction. SPT has a high sensitivity and specificity for the diagnosis of allergic sensitivities. It is well tolerated, carries low risk and delivers rapid results (ASCIA, 2013).
At the Australian Allergy Centre, the standard panel for skin prick testing is the Airborne Allergen panel. This panel is bulk-billed and includes a range of common inhaled allergens including grass, tree and weed pollens, dust mite, mould spores and animal dander. Should it be indicated, the Food Allergen panel can be performed for an additional S150. This panel covers milk, egg, peanut and a variety of grains, seafood, meats, fruits and vegetables. An assorted Nut panel is available for $75, for individuals in which a nut allergy, or allergies are suspected. The panel includes peanut, walnut, hazelnut, pecan, pistachio, almond, macadamia, brazil, cashew and pine nuts.
Note: SPT is not recommended for infants under two years of age, women who are pregnant, or individuals with persistently severe or unstable asthma (ASCIA, 2013).
PREPARING FOR YOUR SKIN PRICK TEST
Some medications can reduce skin reactivity and affect the accuracy of your skin prick test. For this reason it is recommended, oral anti-histamine medications (e.g. Claratyne, Zyrtec and Telfast) are ceased 5 days prior to testing. Likewise, oral steroids (e.g. prednisone) should be ceased 7 days prior to testing. Topical steroid creams, nasal sprays, antibiotics and asthma medications should not interfere with your test results and can be continued as prescribed (ASCIA, 2013).
Please inform the doctor prior to attending your appointment if you are taking any cold and flu medications, anti-depressants, or medications for blood pressure management or migraines. This is important as some antidepressants and cold and flu medications have anti-histamine properties and may interfere with test interpretation. Blood pressure and migraine medications are sometimes contraindicated in skin prick testing, and may need to be withheld for high-risk individuals (ASCIA, 2013).
On the day of your skin prick test please wear clothing which enables easy access to the skin on your forearm and upper arm, and do not apply moisturiser to your arms.
For parents bringing children for allergy skin prick testing, it is encouraged you read "Your child's allergy test. What to expect and how to prepare."
Australasian Society of Clinical Immunology and Allergy [ASCIA], 2013. Skin prick testing for the diagnosis of allergic disease. Accessed 30 July, 2015, http://www.allergy.org.au/images/stories/pospapers/ASCIA_SPT_Manual_November_2013.pdf