When two cultures butt heads, you find a bunch of things that seem obviously right to one person, and just as obviously wrong to the other. Take something as simple as water ...
It's a lot more tricky than our Western upbringing would suggest. I can remember being told to "get out of those wet clothes before you catch your death of cold", but that's about the limit of my instructions with regard to water.
Ever been in Hong Kong when it has just started raining? That stuff must be dangerous, given the lengths that people go to to avoid it. Briefcases and newspapers are prime umbrella-substitutes, with sheets of cardboard also viewed favourably. If there aren't any suitable flat opbjects nearby, hold your hand over your head. Yup, that'll work (hands over mouths are also known to filter out 99.99% of all toxic gases when standing at the traffic lights waiting to cross the road).
I'm guessing that the fear of rain on the head may be related to the problems of washing your hair too near to bedtime. Now it's true that you'll be risking an unmanageable hairstyle if you go to sleep with damp hair, but if you have no shame (or in my case, no hair), that's a risk you're just grown-up enough to take. Not here -- that "wet air" from your wet hair will penetrate your body and do dastardly things.
The whole wet-air view of the world is especially significant if you are pregnant. If you're going to do this whole having a baby thing right, the local recommendation is to avoid bathing for one month after the baby is born. Otherwise, the water will enter your body and cause all sorts of aches and pains in future life. Few women wait the whole month nowadays, much to the mutters and grumbles of their older relations (and silent thanks of their husbands).
How about water that comes out of the taps? Would you drink it? I've been drinking it for ten years, and apart from the scorn of local waiters, it's had little effect so far. If you're born here, I'm guessing the jug of boiled water is waiting there at the ready?
What else have we got... how about sweat? Hong Kong must be the paper tissue capital of the world. We're into the warmer time of year, where men wear vests, and women get dabbing with those paper tissues (often followed by careful inspection, though I haven't yet worked out quite what they expect to find). And the big daddy of all cultural differences, Fung Shui -- Wind & Water. Fung Shui is the reason we have a large fish on the sideboard "to help bring children in the family". Let me see, we bought that in Bangkok nine months ago, and Mrs B is now eight months pregnant....
Make sense ? Not to this ignorant barbarian, but hey, if it works, don't knock it !