Peri-operative anaphylaxis is a rare, severe allergic reaction to a medication given in the operating room (OR). When a patient has an allergic reaction in the OR, the anesthesia / surgical team will typically evaluate the patient for signs of rash / swelling, monitor the patient’s vital signs to assess for lung / airway or cardiovascular involvement, and treat the patient with medications to reverse the allergic reaction. A blood tryptase level is typically obtained soon after the reaction as an objective indicator of an allergic reaction mediated by an immune cell called a mast cell. Two-thirds of cases of peri-operative anaphylaxis are triggered by activation of mast cells by an IgE antibody directed against a medication. The remaining one-third are not triggered by IgE. If IgE is involved, it can be measured by a series of skin tests in the allergist’s office.

What does skin testing for drug allergy involve?

Prior to the appointment, the referring physician will need to provide a complete list of medications the patient was given in the OR so the allergist can choose the right skin tests. Medical records may be faxed to 513-636-5835. Studies have recommended that the optimal timing for drug allergy evaluation is 28 days – 6 months after the reaction. To conduct skin testing, patients need to be off any medications that prevent interpretation of skin tests, such as antihistamines (Benadryl, Zyrtec, Allegra, Claritin, Periactin) and some medications used for depression, anxiety, or seizure control. A skin scratch / prick allergy test is conducted first but may not be sensitive enough to detect all allergens. Many patients require intradermal (ID) testing of each medication as well; ID tests are performed by injecting a tiny amount of the diluted medication under the skin.  

 Are there limitations to skin testing? 

If skin testing does not give a clear answer, the allergy consultants may recommend drug challenges to make a diagnosis or to test for safe administration of a closely related medication. Drug challenges occur in a clinical setting where careful monitoring of vital signs is possible and allergic reactions may be safely treated.