so since i'm allergic to codeine, that means i'm allergic to all kinds of opiates?

I don't understand...

I had an allergic reaction to codeine (itchy rash that last two days) &I read that I should be allergic to all kinds of opiates.

I don't think I am though! I have taken Vicodin and been just fine. As well morphine, also fine.

What gives?

: http://alcoholdrugstreatment.info/so-since-im-allergic-to-codeine-that-means-im-allergic-to-all-kinds-of-opiates