A friend recently commented that she resumed her workout routine of running but found that every time she exercised, her nose began to run and she sneezed constantly for hours afterward. I explained that the problem might be that she was dehydrated. This created a paradox for her. Why would a body that was dehydrated eliminate more water? The answer lies in the body’s water management system.
The human body contains on average about 70% of it’s weight in water. For the average adult, that’s about 10 – 12 gallons. Water is the medium through which all of the functions of your body’s systems operate. Water transports nutrients, hormones and enzymes through out your body. It conducts the electrical currents that run through your nervous system. It lubricates joints, moistens the respiratory system and regulates body temperature. Water is so essential to life that we can’t survive without it for much more than three to six days. That’s because we lose about 3-4 quarts a day through the normal process of sweating, elimination through urine and bowel movement as well as normal breathing. All of that water needs to be replaced each day.
Most people expect the water loss through sweating and urinating, but breathing is often overlooked. We lose about 1-2 quarts of water a day just from breathing! If you doubt this, think of the cloud your breath produces on a winter day. Or the fog that you create on a cold mirror when you breathe on it. That’s water vapor from your body! As the body becomes dehydrated (after about 2% of your water content has been lost), the body begins to activate its water management system: kidneys begin to slow the elimination of waste products, thereby conserving water in the blood stream, digestion slows, body temperature rises and the nose will begin to run.
This leads us to the paradox. If the body is trying to horde water, why would the nose begin to run? Remember we lose at least a quart of water during the day just from exhaling. That water is transferred out of the body through the lining of the nose, bronchial tubes and alveoli of the lungs as vapor. If the body covers the respiratory tract with a mucus coating, which is thicker and more viscus than the water vapor, it can reduce much of the water lost during respiration. The water lost by the dripping nose is inconsequential to the potential loss through vapor during exhalation. It’s a trade off that is worth it in the long run. So that’s why my friend’s nose begins to run. But what about the sneezing?
The primary mechanism of the body’s water management system during dehydration is the neurotransmitter histamine. Histamine is integral to the body’s immune system and triggers inflammatory responses when needed. Inflammation is basically the re-distribution of the body’s water to a localized area to create swelling. This might sound familiar, since many people routinely take anti-histamines to suppress the inflammatory responses to pollens and dust that create an allergic reaction.
When the body is dehydrated, more histamine starts circulating in the blood stream trying to manage the remaining supply of water. This sets up the body to become hyper-sensitive to any trigger (like a grain of pollen or spec of dust) that would cause an allergic over-reaction – like the continuous sneezing that my friend mentioned she experiences.
So my recommendation to her is to increase her daily water intake to 1/2 of her body weight in ounces per day. This is a good rule of thumb for the average person at an average activity level. Someone who exercises more or lives in a dryer climate (like Flagstaff) might require even more daily water. But this is a good place to start. If the symptoms persist after a day or two at this increased level of water intake, then dehydration as a source has been eliminated and other sources need to be explored. But there’s not harm in ruling out dehydration first. Best of all, water is free!