I have the occasional asthma attack. I usually dont have any clue before-hand that I will have major trouble breathing. Sometimes I have drunk an unfamiliar type of beer, other times, I have exorcised in a place with the wrong thing blooming. For just such an occasion, I keep some leaf of Foxes Glove, more commonly known as Jimsonweed or Datura, (and not to be confused with the very different Foxglove) in my wallet, along with some matches. While large doses of the medicinally active principles can cause hallucinations, dehydration and death, the amount taken in the lungs when smoking is not on the same order of magnitude. Usually, one, sometimes two or three inhalations of the smoke, either with a pipe or free air is enough to relax the bronchial tubes, regardless of cause (unless they are coated on the inside with something). The dried leaf burns for a short time and goes out, so hold the flame to it until just before inhaling or while inhaling. The primary action is general tissue relaxant and I have used crushed, fresh leaf to reduce swelling and pain from bee sting and swelling from allergic reaction to mosquito bites. My uses closely parallel certain native American tribes' uses and that found in medieval English herberia manuscripts. I can site sources if any are interested.