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...trouble with mucous linings of nasal pssages dryness that can cause
nazal
bleeding. None are life threatening, but many create a lot of discomfort.

http://www.who.int/ith/chapter02_01.html
http://www.cmhc-schl.gc.ca/en/burema...bhose_ce01.cfm

The sites above mention "discomfort" with low health risks. Then again,
there are other remedies, eg skin ointments, mufflers and saline sprays.

Works for some people, but for a 75 year old person with other problems,
they don't want to play wiht sprays and oitments,



Many sites mention mold problems from higher humidity, and this one

http://www.webcom.com/~bi/formaldehyde.html

says raising the RH in a house from from 30 to 70%
can increase the formaldehyde level by 40%.

Why would anyonw want 70% RH? Most people are very happy wiht 30% to 50%.
Rather than live in a dry uncormfortable environment, other measures should
be taken to eliminagte the causal relationships noted.




As to furniture cracking, my cabinetmaker friend Bob goes to
great lengths to avoid cracks from humidity changes, by design.

Step one is to dry the wood beforehand. Wood moves with climate changes and
has to be considered in design. Extreme fluctuations still happen Museums
presverve furniture by keeping the environment stable year round. Most
homeowners don't have the resurces to do that fine of control. Adding
humidity is one though.

Your friend Bob is making his work in a small region. Furniture build in a
drasticly idfferent climate will have movement when shipped 2000 miles to
another extreme. His perfectly fit chair rung will hold up better over time
than a pefectly fit chair rung in a tropical region and then shipped to a
very dry region.



The cold dry is not as dry as taking that same air and heating it 60 or 70
degrees.

That doesn't change its moisture content.


True. but when you heat the air in a hot air furnace and then vent some of
the air up the flue, you are left with a very dry air and low relative
humidity.