On your allergy list, it is most helpful if you can write down when you became aware of the allergy; the actual occurance or what was happening to you at the time, and the approximate year. This will help your specialist identify whether what you remember as a "reaction" or an "allergy" may or may not influence their decision to try the same or similar drug for another situation you may be experiencing. Example: If you remember as a person in their 20's you were given Codine and you had a case of hives, but you are now 70 and you tend to get hives when you are nervous too, your treating professional may want to try the use of Codine again. It is very important for you to keep accurate information regarding your health history and how it changes.
You can't always use the insert that all pharmacies are required to give you with each prescription as the final word, in that those inserts are created to cover all bases, and usually are drawn up as a form of "legal protection" for all parties involved. Pharmacists are usually very helpful in answering questions regarding any concerns you might have associated with whether or not your current medications may have a reaction with a new medication that has been ordered for you.
We are at a time in healthcare where we have to take personal responsibility to communicate our medical history to any medical professionals that treat us. That history should include allergies to any medications, as well as things like latex. The information needs to be in writing as well as explained verbally. Make sure you are consistently telling all of the medical professionals treating you, what your allergy history is! "Now let's get going!"