Asthma treatment post-collapse
Asthma has been treated by healers since the earliest written healing record. We have documented recipes for breathing treatments and herbal remedies by the Greeks, Egyptians, Chinese, etc, and probably it meant any chronic breathing issue. Most likely it's always been treated before the invention of a written language.
That doesn't mean they lived for very long unless they had those treatments, for one can get a serious allergic attack, and suffocate since you can't get enough oxygen, and pass out and die.
Only in the foolishness of the early 20th Century was it labeled as a psychosomatic illness and it wasn't until the 1960's that again it was recognized as a true medical issue. How absurd we are!
If you or your loved one has asthma, you're probably very concerned and prepping for it. That is wisdom. Still, those supplies will run out, so that means taking the time to learn about the historical means of treatment. Otherwise, you've only postponed a decline in your ability to breathe.
For most Americans, the easiest way to deal with breathing issues is very limited use of jimson weed. [link to medplant.nmsu.edu
One must be very very careful using this herb. Like many plants, it contains an alkaloid, and it can be used for brocodialation (open the brochial tubes that lead to the lungs). It has a potential for abuse, so since in a collapse people will be looking for ways to band-aid their stress, a shaman must be vigilant to protect the community.
For people living on the islands of Hawaii, eating pineapple can help some, for bromelain is derived from it. It's used by runners and some people with breathing disorders to assist them, but in some people it worsens their breathing. Use caution and common sense.
There are many herbs with have a brochodialator effect. See:
[link to www.rosenlake.net
Since much of the issue is allergies, then treat the issue by removing the allergen. Sigh.
One way of treating allergies is taking stinging nettles. While externally, they can cause an allergic skin reaction, they can be consumed as food or tea if prepared correctly and provide not only Vitamin C, but a natural antihistamine effect. Since you won't have Zyrtec, you've got to find ways to treat the root cause of your asthma.
The main means of heating homes post-collapse will be wood fires in rocket mass stoves. While this way is vastly superior (8 x more efficient and mostly steam exhaust versus lots of carbon and fumes), this will still cause an issue for asthma sufferers. Your best bet is controlling your temperature by living underground to naturally raise the temperature to about 50deg F and layers of clothing. Of course, that has it's own issue with potential mold spores. There's no perfect solution.