I wonder if the splendid people who organise BIOMCH-L will
censure me for posting this, a little off the beaten track of more usual
discussions. (I hope not !)

It is apparent however than many of the subscribers to this list know a
lot about joints, there are experts on physiotherapy and perhaps also
rheumatology. This is why I am seeking to use this forum

In the U.K. it is commonplace for people who suffer from what loosely
may be called rheumatic conditions to be aware that in wet weather their
symptoms are worse. This is I think an almost universal observation.

But what is the cause of this ?

A medical scientist I greatly respected thought that because of the low
atmospheric pressure associated with rain that tiny bubbles formed in
the joint tissues. It was according to him like a minor attack of the
divers bends (caisson disease). This sounded at first plausible. However
aircraft cabins are not fully pressurised, and the change after take off
is more rapid than is usual with fluctuations of the weather. I have not
heard of people complaining about rheumatic pains on aircraft.

An alternative position is that with high humidity less water will be
lost from the lungs, and by insensible perspiration from the skin. There
will be some decrease in the osmotic pressure of the blood., which may
perhaps cause cells to swell. However this would surely be quite small.
I wonder if anyone knows of any data about fluctuations of plasma
osmotic pressure according to the weather ?

What else can be the cause ? Any suggestions ?

There is a literature about air ionisation. What I have found difficult
to follow and perhaps questionable because there seems to be no very
satisfactory way of getting measurements. Rain drops will, I suppose,
often have an electrical charge. So what ?

People find rainy weather in Northern Europe depressing. I am loathe
however to consider that the effects is purely psychological.

If the high humidity somehow is the cause, what happens in subtropical
and tropical countries in the wet season ? I have never been to Florida
but imagine that at certain times of the year it is hot and humid. Is
this bad for people with joint problems ? Or is it only the combination
of wet and cold which is the trigger in temperate climates.(even though
most houses now have central heating

Finally if dampness is the main problem, whatever the mechanism, has
anyone tried using a dehumidifier in their house ?

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