What is my legal recourse if a doctor prescribed me a medication that I was allergic to?

Malpractice is negligence. Negligence is the failure to exercise due care (that degree of care that  in this case a reasonable doctor in the community would have exercised under the same or similar circumstances to prevent foreseeable harm).

Since the doctor had notice that you were allergic to the medication, but gave it to you anyway, you would have a claim for negligence against the doctor.  You should obtain your medical bills, medical reports and documentation of any wage loss due to your allergic reaction.

Compensation for the medical bills is straight reimbursement.  Compensation for wage loss is straight reimbursement.  The medical reports will document the nature and extent of your injury (allergic reaction) and will be used to determine compensation for pain and suffering.  Compensation for pain and suffering is an amount in addition to the medical bills.

Prior to filing a lawsuit for negligence against the doctor, it may be possible to settle the case with the doctor's malpractice insurance carrier.  Your claim will include the medical bills, medical reports and documentation of wage loss.  If you are dissatisfied with settlement offers from the insurance carrier, reject the settlement offers and file your lawsuit for negligence against the doctor.  If the case is settled with the malpractice insurance carrier, NO lawsuit is filed.  If the case is NOT settled with the malpractice insurance carrier, you will need to file your lawsuit for negligence against the doctor prior to the expiration of the applicable statute of limitations or you will lose your rights forever in the matter.