Question: If I am allergic to a drug, does that mean I can never take that drug again?
Answer: If you've been diagnosed with a drug allergy, in most cases you should never take that drug again. There may be rare instances when that drug would really be the desired treatment for a particular condition that you may be diagnosed with. In that setting, your physician may elect a very specialized procedure to allow you to take that medication. This process is done typically in the inpatient setting, such as a hospital or perhaps in a clinic where there are trained professionals ready to put you through that process.
However, this is again the exception and so in most cases you should not take that drug again unless you're under the care of a physician who is aware of your drug allergy.