A few common allergens used for skin prick testing will confirm or exclude the presence of atopy in the vast majority of patients.
Uses
Allow diagnosis (or exclusion) of atopy
Provide supportive evidence (with clinical history) for diagnosis
(or exclusion) of allergy
Educational value, providing a clear illustration for patients that
may reinforce verbal advice
Essential when expensive or time-consuming allergen
avoidance measures, removal of a family pet, or
immunotherapy, are being considered
Serum allergen-specific IgE concentrations generally provide
the same information if skin tests are unavailable
Practice Points
Skin prick testing requires training, both for performance and
interpretation of results
Check that patient is not taking antihistamines
Oral corticosteroids do not (significantly) inhibit skin prick tests
Include positive (histamine) and negative (allergen diluent)
controls
Skin prick tests may be performed on the flexor aspect of the
forearm (or back) using sterile lancets (see picture)
The procedure should be painless and not draw blood
A positive test (arbitrarily) is 2 mm or more greater than
negative control. A positive skin prick test is usually at least
6 mm when concordant with clinical history of sensitivity
Demographism may confound results (although it is evident as
a positive response with the negative control solution)
Skin tests should not be performed in the presence of severe
eczema
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