I live above someone who uses drugs. Im not sure if its meth or crack. I only know that I have epilepsy and each time I smell the fumes I have some serious effects from it. How do I know if this is detrimental to my health or temporary or a concern at all

Move... and/or call the cops. Obviously its something to be seriously concerned about. Both are very dangerous.

If you're having serious effects from it (your words), than it's detrimental to your health.

As a person with epilepsy as well, I would be highly concerned, particularly if you live alone, but even if you don't. The next time it is an active condition, consider calling 911 and getting EMS on site, to assess your condition. Not to mention, that if they smell/suspect illegal activity, I assume the police would also be contacted.

Aside from serious potential health concerns, if there are fumes... I would also be concerned about them blowing up the place. You don't know if they are just using or if they are actively cooking something down there, below where you live.