Why does heroin use cause vaginal odor?

It does not. Heroin does not cause a vaginal odor it is a vaginal overgrowth and it is pure coincidence and if you would like to know more I would be happy to consult with you.
It should not. If you have vaginal odor it is more likely from infection. Please see a doctor for an exam and testing. Some vaginal infections can progress if not treated promptly.