Regarding any drug allergy, it's important to know if you have a true allergy or just sensitivity. A real allergic reaction usually causes a rash, especially hives (raised, red, itchy welts). More serious reactions can lead to anaphylaxis (facial and airway swelling, a decrease in blood pressure, and other symptoms). Patients who have true allergic reactions need to make sure all health care providers are aware. Sensitivity may include nausea, vomiting, head ache, itching (without rash), or similar symptoms. Patients should avoid these medications because of these symptoms, but this is not an allergic reaction and therefore not dangerous.Sometimes patients may not be sure of what their reaction was, or even what the causative medication was, because the episode happened in the distant past. Explain this to your doctor.Finally, codeine more commonly causes sensitivity than allergy, but if you had an allergic reaction, other narcotics can still be used with care. There is a low incidence of cross-reactivity, but all narcotics are morphine derivatives and therefore similar. Discuss with your surgeon and pharmacist.Good luck.