The millions of tiny bubbles at the business end of your lungs are amongst the most specialized tissues in your body. In order to permit fast exchange of gases between your blood and your breath these bubbles consist of only two skins, each of which is no more than a single thickness of cells stretched very thinly. This makes them extremely delicate and vulnerable, but so absolute is their dedication to this one function that they can do nothing else, least of all defend themselves. The merest whiff of solvent, acid, detergent or smoke can destroy them totally. So they are carefully guarded by a series of defences stationed at intervals along your airways.
Your nose not only conditions air to your lungs’ liking, but alerts you to many airborne threats, and may trigger extra defences — mucus secretions, sneezing and nasal congestion — as well as making you want fresh air.
These defences are perfect for normal conditions but can be overwhelmed by sustained challenges and by-passed altogether by newly-invented chemicals we do not yet know. Then defences lower down become important.
Your wind-pipe and its rigid branches do their best with rather ineffectual coughing and inflammation. Your smaller airways, muscular and capable of shrinking their calibre almost to nothing, add this last desperate ploy to the defence of your vital gas-exchange skin. Except in very brief encounters this is futile, but your intention is clear enough.
This is the basic process of asthma, which is mobilized in anyone by a challenge strong enough. Allergic people are peculiarly sensitive to a limited range of particular allergens as personal idiosyncracies, but all of us react in some way to obviously irritant or poisonous fumes, even in very small amounts.
Thousands of chemical irritants are already widely prevalent and ten new ones are being introduced each week. Some of them like the organochlorine insecticides accumulate in your body fat and reduce your immune resistance to everything else.
If you are well defended your nose bears the brunt, as rhinitis or sinusitis. Stubborn coughing means challenges have penetrated as far as your voice-box and wind-pipe. Asthma implies the deepest encroachment, all the way down to your smallest bronchial tubes.
Any of these symptoms can also be provoked from within. Your bronchial muscle and nasal skin react similarly to anything, whether in the air you breathe or in your blood.
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