Be Cautious About Dehydration; Its Still Hot Humid Out There

Heli J. Roy  |  6/10/2005 12:37:58 AM

News Release Distributed 10/10/02

People working outside – whether with routine fall chores or cleanup after the recent storms – need to be cautious to avoid becoming overheated or dehydrated, says LSU AgCenter nutritionist Dr. Heli Roy.

"Dehydration can occur when people are outdoors in hot climates doing physical labor," Roy says, adding, "We think of dehydration from exertion happening only with those who engage in sports, but it can also occur in farm workers, construction workers, gardeners and anyone not used to working outdoors for an extended period of time."

The LSU AgCenter nutritionist explains that sweating is a way for the body to attempt to cool down in hot climates and when we do physical labor. But, of course, the loss of body fluids through sweating can increase the chances of dehydration.

"Your body will try to cool down through sweating, so you need to make sure you take in enough fluids to compensate for that," Roy says, explaining that people in the South face an even greater challenge.

"In the southern United States and other areas of high humidity, the rate of sweating is higher in humid conditions but the cooling is less," she explains. "The reason is that since the air is already very saturated with water, sweat can't evaporate. So high humidity can be an additional risk of dehydration."

Roy also says some medications interfere with cooling. Certain drugs may cause dehydration or interfere with sweating. For example, antihistamines and some blood pressure medications decrease sweating. Caffeine and alcohol are diuretics and thus cause your body to lose water.

"Remember that most of the dark-colored soft drinks contain caffeine, so avoid them if possible when you’re working outdoors," Roy advises.

Mild signs of dehydration are increased thirst, dry lips and discomfort. Moderate signs are nausea, sunken eyes, increased body temperature and difficulty in concentrating. Signs of severe dehydration include weakness; mental confusion; a rapid, weak pulse (more than 100 at rest); cold hands and feet; rapid breathing; blue lips; confusion; lethargy; and muscle spasms.

"Keep in mind that dehydration can start before we even get thirsty," the LSU AgCenter nutritionist cautions, explaining, "Increased thirst is a response to a loss of body water, but in order for us to stay hydrated, we need to start replacing lost fluids before first signs of thirst."

Roy says mild dehydration occurs with less than 3 percent loss of body water.

"At that point, we start feeling thirsty, but we have already lost quite a bit of water," she says, adding that at 5 percent water loss, a 180-pound man will have lost 9 pounds of weight because of water loss.

"The signs of dehydration will get more severe with each percentage point loss of body water after that, and dehydration can lead to death at more than 10 percent weight loss caused by water loss," Roy cautions. "At the severe stage, fluids must be replaced by intravenous application.

"To replenish adequately and prevent dehydration, drink extra fluids all day when working outdoors in hot climates – before the first sign of thirst."

Roy says about 4 fluid ounces to 8 fluid ounces of water consumed every 15 minutes to 30 minutes is recommended during heavy activity in hot climates. To replace all fluids lost, 2 cups of fluids are needed for every pound lost.

"The temperature of the replacement fluid is not critical," the LSU AgCenter nutritionist says, adding, however, "Some studies suggest that fluids at room temperature may actually pass through the intestinal cell walls faster and replace lost fluid in the cells faster."

Whether or not plain water or an electrolyte solution is used is not critical either, according to Roy, who stresses it is the total volume of fluids consumed that is the critical factor.

Dehydration also can occur during illness when there is severe vomiting and diarrhea or in individuals with diabetes, kidney disease, excessive use of diuretics, liver disease resulting in accumulation of fluid in the abdominal cavity, inflammation of the abdominal cavity resulting in fluid accumulation, and burns.

To prevent dehydration, Roy offers these tips:

–Use light-colored clothing that reflects light and is of loose, lightweight material. Tightly woven clothing does not allow heat to pass through. Some synthetic clothing made today is made for the purpose of allowing sweat and heat to be pulled from the skin.

–Adapt to the heat. Heat acclimatization is a process by which the body makes adjustments to promote better cooling in hot environments. In that process, sweat becomes more dilute and your body learns to hold on to salt. The threshold at which sweating begins also is lowered, and the sweat rate is increased. These changes take time to complete fully – about 10 days of high activity in the heat – and will work only if you are well hydrated. Make sure that you are properly adapted before going out.

–Check with your doctor about the medications you are taking. Since certain drugs may cause dehydration, check with your doctor if you can avoid their use for several days prior to being outdoors doing physical labor. And ask if you should be outside in the heat at all.

–Drink before, during and after being outdoors. Hydrate thoroughly the day before if you can. A good sign of hydration is the output of large volumes of clear, dilute urine.

–Hyperhydrate just before going out. Drinking approximately 1½ to 3 cups of cold water or an electrolyte solution can help delay the process of dehydration.


Contact: Heli J. Roy at (225) 578-4486 or

Rate This Article:

Have a question or comment about the information on this page?

Innovate . Educate . Improve Lives

The LSU AgCenter and the LSU College of Agriculture