Penicillin Skin Testing:
Indicated in patients who have a reaction history consistent with a possible lgE-mediated mechanism.
99% effective in predicting penicillin allergic reactions if both the major and minor determinants are used. The major determinant (benzylpenicilloyl-polylysine [PRE-PEN]) is commercially available. The minor determinant mixture (penicilloate and penilloate) needed for the test is available via TPD Special Access Program. However, skin testing has several limitations to its use:
Only predictive of IgE-mediated allergic reactions to penicillin (not cephalosporins).
Skin testing with major determinant and penicillin G 10,000units/mL only may miss up to 20% of allergic patients.
Although usually safe, fatalities have occurred when done improperly. Therefore, penicillin skin testing should only be performed and interpreted by a qualified allergist.
Skin testing should NOT be performed for patients with a history of:
severe cutaneous reactions [e.g. SJS, TEN, exfoliative dermatitis, AGEP, acute generalized exanthematous pustulosis (AGEP), DRESS]
Patients with negative skin test results to penicillin major and minor determinants may receive penicillin with minimal risk of an IgE-mediated reaction.
Patients with a history of penicillin allergy but negative skin test results are NOT at increased risk for cephalosporin allergy and so may receive these drugs.