You know, steroids.
I just took my first dose.
As you may be able to guess, I have asthma. I thought I had asthma, but no, I have asthma.
It would seem I have been very stupid for three reasons:

1) Not having my "childhood" asthma checked up on regularly.
2) Not going to the doctor on previous, more recent, occasions when I have shown asthma symptoms.
3) Not going to the hospital last night, because today's peak flow reading was pretty bad, and gosh darn it, I could've died.

Had an awful night's sleep last night, due to inability to breathe.
Okay, so an inability to breathe seems like a pretty reasonable thing to rock up at the emergency department for, but what can I say? I'm an idiot.
So now I'm on Fluticasone twice daily (preventative steroid) and Salbutamol as needed (aka Ventolin).

Beware, I now have a renewed reason to bitch about your smoking!