Here's a theory as to the cause of asthma which is not currently being researched. It would be interesting to hear your views.
Asthma arises because we put bleach (Sodium Hypochlorite) down the toilet; we leave it to do its work, sometimes overnight, we then, too often, use the toilet without flushing it beforehand.
The mix of urine (containing ammonia) and bleach reacts to give off a small dose of Chloramines which we breathe in and which causes the damage to our lungs.
Repeated regularly the damage becomes significant. Our damaged/weakened lungs become less hardy and more sensitive to our environment. Triggers that we would not previously have reacted to suddenly begin to affect us more. For some, exposure to these triggers leads to an asthma attack.
This theory is supported by evidence linking asthma to the levels of hygenie in a household and to evidence linking asthma to swimming pool users.