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The importance of healthy humidity

If there's one - okay two - things you can do to improve your general health and susceptibility to colds this year it's this.  Get a vaporiser.  And use it daily.
Firstly, what is a vaporiser?  A vaporiser is an electrical device that runs from a power point (using about the same energy as a kettle or toaster).  A fully contained heating element inside heats the water inside the chamber, which is then pushed out through vents and flows into the room as warm invisible droplets of steam.   And why do you need it?  Here’s the low-down.
Humidity: your body’s friend 
Leonardo da Vinci said “Water is the driving force of all nature”, and he wasn’t wrong.  The typical adult body is made up of 50-60% water, and without it, we literally wouldn’t exist.
Water assists a whole host of vital bodily processes including circulation, digestion, metabolism and temperature regulation – not to mention keeping healthy our main line of defence against colds and flu, the protective mucous membranes which line the mouth, nose and throat.
These membranes are a glue-like blanket of mucous which effectively traps inhaled particles (ie. pollen, cigarette smoke, viruses and bacteria) when they adhere to its surface.  Tiny moving fingers called ‘cilia’ then expel these particles.  Every time you cough or sneeze you have this complex system to thank for ridding your body of a potential invader.   It’s pretty clear the importance the mucous membranes play in helping ward off sickness, but they require one thing to keep them working at optimal potential – moisture.
Dangers of low humidity
Even a slight reduction in humidity levels can compromise respiratory function – cilia slow down their activity at 70% humidity and stop working entirely if it drops below 30%.  
According to research published in Environmental Health Perspectives, maintaining proper humidity levels may help to lower the rates of respiratory infections and allergies. 
Studies have also shown that airborne bacteria and cold viruses live longer at low humidity levels – particularly below 40%.  
So what’s the best “healthy” level?  Most experts agree that a humidity level between 40-60% is ideal but - especially in winter - most homes will need some help.
What’s your home’s humidity level?
Average indoor humidity in the drier parts of Australia may drop as low as 9% in winter and commonly hovers around 15-20%.  

For an accurate reading, you can use a device called a hygrometer (try electrical retailers like Dick Smith, hardware stores or eBay).

Why is low humidity such a problem in winter?   At a molecular level, colder air simply holds less moisture, while hot air can hold more.  Plus, indoor heating and air conditioning also has the effect of stripping moisture from the air, increasing the drying effect.
It’s not just about colds
Low humidity not only affects your ability to fight off colds, it can have a whole other host of unwanted effects as well.  These can include dry skin which is more prone to visible fine lines, irritated sinuses and throat, itchy eyes.  Long periods of low humidity can also affect furniture, as it causes wood and adhesives to dry out.
Get steamy indoors – and save money
Running a vaporiser indoors while you relax, watch TV, sleep at night or even in the office while you are working is an easy way to increase relative humidity to healthy and comfortable levels.  Vaporisers are very economical to run, and may in fact even save you money in winter, as higher humidity makes the room feel warmer (because sweat cannot evaporate as easily from your skin).  
This could enable you to lower your thermostat a degree or two making big savings on your heating bill.
  For more information on vaporisers ask your local pharmacist or any of these outlets.
US Pharmacist Oct 1999
Indirect health effects of relative humidity in indoor environments. Arundel et al, Environ Health Perspect. Mar 1986;65: 351-361.