Making
sure your body has sufficient water will not only
counter the overall dehydrating effects of air travel, but can actually fortify
your first line of natural immune defense mechanisms to function considerably
better. It will also help to 
counteract the effects of jetlag.
However, in an airplane, where your nose and
throat are on the front lines of the war with exceedingly dry air, these are
the first places to suffer. This protective system, called the Mucociliary
Clearance System, is your first line of defense against harmful germs and
bacteria. If the common cold is pounced on by a sufficiently moist and active
mucosal layer in the nasal passages, you have a better chance of remaining
uninfected. If these systems are impaired, you will be suffering within days.
Colonic hydrotherapy is actually the most effective way to hydrate the body, even more so than when we drink. This is because we are bypassing the digestive tract and going straight to the ‘source’ as it were. One of the large intestine’s (colon’s) main roles is to control the fluid balance of the body by osmosis through the wall of the intestine. This is why, when we don’t answer the call of nature often enough, the fecal matter which is left behind becomes harder and dryer, because the body has decided that the hydration was needed more importantly elsewhere in the system.
Sipping water or some other good quality fluid (such as herbal teas), regularly throughout the flight will help to maintain this hydration and counteract the effects of the flight. Additionally, hot drinks are a good way to keep your protective mucous membranes working. They will help in triggering the system into gear by directly providing moisture in the form of steam. This will support your nasal passages protective mucosal system from long dry spells. (Alcohol and caffeinated drinks such as coffee or soft drinks can actually dehydrate you, so avoid these as much as possible.) Nasal mists have also been found to be very effective in keeping this system working in your nose. However, you will be missing out on the overall benefits of being hydrated if you rely solely on this method.
Studies have concluded that a likely cause of the increase in the transition of the cold virus is the extremely low cabin humidity, which is caused by low humidity at high elevations. It was also found that aircraft that actively re-circulated air actually showed slightly lower transmission rates than those that did not.
Most commercial airlines fly in an elevation range of 30,000 to 35,000 feet, where humidity typically runs at 10 percent or lower. At very low levels of humidity, the "natural defense system" of mucus in our noses and throats dries up and is crippled, creating a much more susceptible environment for germs to infect us.
This approach to supporting your immune defenses with hydration can be taken into every day life and by keeping yourself hydrated when working in any air conditioned environment (including the car), as well as any other situation where you are likely to become dehydrated, such as at the gym, you may help significantly reduce your susceptibility to infection. Another thing to remember is to make sure that you keep your hands away from your face as much as possible as germs are easily transmitted from your hands to your nose and eyes by direct contact.
Enjoy your travels!!
