Age: How long ago did the patient’s reported allergic reaction to penicillin occur? How old was the patient at the time of the reported allergic reaction? | The longer the time elapsed since the reaction, the lower the likelihood that the patient will experience an IgE-mediated reaction, as patients can outgrow hypersensitivity reactions with time. If the patient was very young at the time of the reaction, he or she may have learned of it through information relayed by family members, which increases the risk of historical inaccuracies. |
Administration of penicillin: How was the penicillin administered? | The parenteral and cutaneous routes are thought to confer greater risk of sensitization than oral administration. |
Symptoms: Did the reaction include hives, throat swelling, diarrhea, vomiting or shortness of breath? Were other organ systems involved? If the only symptom was a rash, what was its distribution and pattern? | It is important to differentiate symptoms reflecting a true IgE-mediated allergy from less serious or sometimes more severe (e.g., Stevens–Johnson syndrome) non–IgE-mediated reactions. If the reaction consisted solely of a rash, non–IgE-mediated causes should be carefully considered. |
Timing: How long after the penicillin was administered did the onset of symptoms occur? | It is important to identify the temporal relationship between drug administration and onset of the reaction. Most IgE-mediated reactions occur immediately (within one hour), whereas substantial delays between administration and reaction suggest a non–IgE-mediated drug reaction or another alternative cause for the symptoms. |
Other medications: Was the patient taking other medications when the penicillin was administered? If so, what were they, and when were they taken in relation to the reaction? | Penicillins are often given in conjunction with other medications, and it may be one of the other medications that is the real precipitant of the reported reaction. |
Previous reactions: Has the patient had previous reactions to other medications? | Some patients may have documented reactions to related drugs (e.g., cephalosporins, carbapenems), which may indicate that they are at risk of a severe reaction if penicillin is administered. |
Exposure to β-lactam antibiotics: Has penicillin or any other β-lactam antibiotic been safely administered to the patient either before or after the reported reaction to penicillin? | Subsequent exposure to penicillin without a reaction suggests that the patient does not have an IgE-mediated allergy. It is also important to determine whether other β-lactam antibiotics have been safely administered. |