On the road again. (Executive Health Package).

REGINA GREER CRISSCROSSES ALMOST 23 STATES as the business service manager for American Water Company, based in Fairview Heights, Illinois. In fact, she's racked up more than 100,000 frequent-flyer miles.

"You don't always feel your best, but you have to go," says Greet, 31. You can't always combat the health hazards associated with travel, but you can take definitive steps to stay as healthy as possible.

FLYING

Closed quarters, fluctuating air pressure, and time changes can contribute not only to the symptoms of jet lag (irritability, inability to concentrate, diarrhea, constipation, and swollen ankles) but also to colds and sinus problems. "People underestimate [jet lag's] effects," notes Dr. David Freedman of the University of Alabama's Travelers Health Clinic in Birmingham, Alabama. "In fact, some large companies forbid their top executives to sign contracts or to make any major decisions until several days after arriving, so their bodies can adjust."

REDUCING THE ADVERSE EFFECTS OF FLYING

* Watch your medication. Avoid unnecessary, nonprescription medication, which becomes more potent at high altitudes.

* Keep hydrated. Cabin air has no humidity, so people tend to lose water. To combat dehydration, drink lots of water and reduce alcohol and caffeine intake.

* Eat light. A large meal before or during a flight will cause lethargy making it more difficult to cope with jet lag.

DEEP VEIN THROMBOSIS 

Another concern for long-distance travelers is Deep Vein Thrombosis (DVT), which occurs when a blood clot forms in the body as a result of prolonged sitting--on a plane, in a car, or on a train. It can prove fatal if the clot travels to the heart, lungs, or brain.

Here's how to prevent DVT:

* Stretch. For flights longer than two hours, stretch at regular intervals. There are a number of exercises that can be done while sitting. Diana Fairechfid, a former flight attendant and the author of Jet Smarter (Flyana Rhyme; $14.95), offers stretching exercises on her Website, www.flyana.com.

* Dress comfortably. Avoid tight-fitting clothing as it can restrict circulation.

* Give yourself room. Remove any hand luggage that blocks foot movement.

INTERNATIONAL TRAVEL

International travelers may want to consult a Travel Medicine (TM) physician. 'The illnesses associated with foreign travel change over time," explains Dr. William Burmeister, a TM physician based in St. Louis, Missouri. "Patients have died because they weren't diagnosed quickly enough or because their doctors weren't aware of diseases associated with a foreign country." Furthermore, treatment for a disease like malaria in one region may be totally ineffective in another. A TM physician can alert travelers to immunizations required for a particular destination. To contact a TM doctor in your area, go to the International Society of Travel Medicine Website, www.iztm.org.