There are a couple things which cause those irritating dry coughs which plague you at certain times. Do you have a problem coughing while in bed or wake up coughing? Do you have one of those nice, soft velvety velour blankets on your bed? I discovered those little velvet hairs on the blanket shed while you are sleeping and you inhale them. That is one of the things that can cause coughing episodes because it irritates your throat… and who knows what it does to your lungs. Washing doesn’t seem to help. As much as I loved those velvety blankets, I had to get rid of the blankets entirely. I would wake up in the middle of the night in a coughing fit, not realizing what the source was. I got rid of the blanket which got rid of the coughing. However, you may have other blankets or sheets shedding some type of fiber while you are sleeping. Even dust on you bed can start a coughing fit if you inhale it while deeply sleeping.
Another source of coughing can be those cheap carpets which shed. Are you constantly seeing carpet fibers while you are vacuuming? These types are short staple fiber carpet which will continue to shed and fill your house and lungs and filters with fibers until you finally remove it and buy a continuous filament carpet which does not shed. When selecting a new carpet, rub your hands over the new carpet and roughly rub it briskly to see if any fibers come loose… before you buy. Here is a link about this problem. http://www.homecarpetshopping.com/why_do_carpets_fuzz.htm
The onset of coughing and watery eyes can also be a warning that you need to change your furnace filter. You should change the filter every month. If you think that is too expensive, I can remind you that a doctors office visit for a cold or lung infection will be far more expensive than a new filter once a month. My filters are far more expensive $20-40 each. But I change them every month… no more than 2 months even though they claim they are good for a year. If you have birds, pets and children, the filter will clog up much faster.
Anytime you get those irritating dry coughing episodes, start looking around for the source of irritants in the air. If it happens in a particular place such as a bed, then the source is likely in your bedding. Or it could be fuzz from your furniture. Placing sheets on your furniture can help reduce shedding fibers.
Fiberglass or draperies can also be other sources of irritants. Or it could be from some other source. Some items can be dangerous to your health such as fiberglass, asbestos, molds, etc. Make sure you do not have any exposed insulation or insulation inside of your central air vents blowing hazardous fibers around your house. There are also areas in your house which may not be dusted such as above your kitchen cabinets or ceiling fans, etc.
You should also check your dryer vent to make sure the vent exhaust has not come loose or your dryer has not become plugged with lint. Always be sure to clean your lint trap every time you use your dryer. Check inside the dryer to make sure the vents inside the dryer are not plugged up.
Even those velvety clothes can shed fibers you could inhale.
These are just a few ideas. Fibers could be shed from anything… or it may be mold spores. Or it could be mice in your house after dark or insects.
These are just a few sources I could think of off the top of my head. You may need to have a professional test your house for airborne irritants which could be hazardous to your health.