I have a severe morphine and oxicodone allergy. I am also allergic to several NSAIDS and most over-the-counter NSAIDS, while producing no allergy symptoms do not provide pain relief. I am having surgery and they want to use a drug call Tramadol which has Tylenol in it's formula. I've never gotten pain relief from Tylenol. I copied the article which states there are 3 different classes of opiods. If I am allergic to the ones in the phenanthrene class, can I take a drug from the other two groups and not have an allergic reaction such as swelling and/or severe pustules and itching?