Dealing with the occasional bout of diarrhea or constipation is never fun, but the most inopportune time to experience digestive problems is while traveling.

"Traveler's diarrhea is the obvious example," says Dr. Eamonn Quigley, a gastroenterologist at Houston Methodist. "But this usually thought to be limited to travel in certain areas of the world where gastroenteritis risk is high."

It's certainly something to know about and take steps to prevent, but Dr. Quigley points out that diarrhea while traveling can occur anywhere and be completely unrelated to infection.

"What most people don't realize is that constipation is actually the more common gastrointestinal phenomenon that arises during travel," says Dr. Quigley. "The No. 1 reason for occasional constipation is travel."

These aren't the only two GI problems that seem to arise. You might find you're more likely to get heartburn while away from home. Flying might leave you feeling bloated and gassy. And we're likely all familiar with the nausea that can sometimes accompany a car, boat, or rollercoaster ride.

All to say, the digestive system seems particularly sensitive to travel and its related activities. But why? And are there steps you can take to make sure your bowel movements stay regular and stomach remains settled while on a trip?

10 causes of stomach problems while traveling

"There are several things that can lead to digestive issues while flying, specifically, and traveling in general," says Dr. Quigley. "And people prone to constipation, diarrhea and other GI issues might be more easily triggered by these factors."

An important note: They can also be additive, meaning these factors can compound on top of one another to make problems more likely.

The reasons for experiencing stomach issues while traveling include:

1. Dietary changes

Our diet and eating habits often look different than usual while traveling. Away from home, we're less in control of what we eat and when we eat. We might treat ourselves to snacks and desserts more frequently on vacation.

"Maybe we're eating fewer vegetables and therefore getting less fiber, which can lead to constipation," says Dr. Quigley. "Or sometimes we're trying entirely new cuisines and we inadvertently eat something we're intolerant of and diarrhea or indigestion result."

Not overeating and maintaining a balanced diet as much as possible can go a long way toward avoiding these fates. But that's not always totally realistic during travel, especially when you're trying to enjoy your vacation. This is where Dr. Quigley recommends knowing which over-the-counter medication to take if you do experience a digestive issue.

• Anti-diarrheal medications (loperamide, bismuth subsalicylate) can help reduce the frequency of watery, loose stools
• Oral laxatives and stool softeners (polyethelene glycol, docusate sodium) can help alleviate constipation
• Antacid pills can help with heartburn, indigestion and upset stomach

Be sure to take these medications according to the package instructions.

2. Stress

The stress of travel can begin soon after you leave the house: Making sure you don't miss your flight, navigating a crowded airport, needing to evacuate your bowels in a bathroom you share with people sometimes sitting inches away from you.

"Stress influences bowel function, which can go either way — constipation or diarrhea," says Dr. Quigley. "All you have to do is think back to that important exam you had in college to remember how stress can make bowel movements more frequent or loose. But stress can also lead to incomplete bowel movements in other scenarios."

Back to that cramped, shared bathroom on a plane: The ensuing stress can prevent a person from having a complete bowel movement, which can contribute to constipation. Plus, when constipated, people tend to fixate on the issue, notes Dr. Quigley, adding to the stress and making the constipation worse.

Here again, there's not always a lot you can do — travel is just stressful sometimes. But the same advice as above applies: If you do experience diarrhea or constipation while traveling, the right over-the-counter remedies can help relieve it.

3. Dehydration

Being dehydrated is a risk factor for constipation, but drinking enough water while traveling can be tricky.

(Related: How Much Water Should You Drink In a Day?)

Bathroom breaks can be time-consuming on a long road trip or tricky to accommodate in certain locations, leading you to purposefully drink less water. In addition, a supply of water isn't always readily available while traveling — or that supply might not be safe.

Dr. Quigley stresses the importance of having a hydration plan while traveling, whether that's bringing a water bottle you can fill yourself or knowing where to buy sealed water that's safe.

4. Alcohol consumption

"We should hydrate with water, not alcohol," Dr. Quigley adds. "Whether it's a drink before a flight or at lunch between sightseeing, know that alcohol is not hydrating."

In fact, alcohol is dehydrating — and remember, dehydration is a risk factor for constipation.

5. Barometric pressure changes

"Airplanes have pressurized cabins, but they're not completely pressurized," says Dr. Quigley. "The greater the difference between the pressure in the atmosphere and that in your body, the more the air in your stomach is going to expand — and that's why you begin to feel bloated while flying."

Bloating is annoying enough on its own, but if it persists, it can also contribute to constipation.

"The longer the flight, the more noticeable the issue can become," says Dr. Quigley. "Studies show that long-haul cabin crews experience more gut disruptions than short-haul crews."

Now is a great time to point out just how additive some of these factors can be, especially with certain types of travel. For instance, flying is often a triple whammy — stress, dehydration and pressure changes are a recipe for experiencing constipation while traveling if you're not careful, especially if you're already prone to it.

"Add to that the carbonated diet soda you have before or during your flight, which only makes bloating worse," says Dr. Quigley.

6. What you eat and drink before a flight

The gassier your meals and beverages are before a flight, the more likely you are to get bloated and constipated.

"Avoid eating foods that are most likely to cause gas, like onions and garlic, for about 24 to 48 hours prior to flying — since these take quite a while for your body to completely digest," says Dr. Quigley.

Carbonated soft drinks and sparkling waters are another cause of bloating. In some people, they can also trigger indigestion while flying. But since liquids pass through the body quickly, they're typically only an issue when consumed shortly before boarding a flight.

7. Traveler's diarrhea

Traveler's diarrhea — a type of gastrointestinal infection — occurs when a person gets ill from food or water that's contaminated with a virus, bacteria or parasite. The primary symptom is indicated by the name, but traveler's diarrhea can also cause abdominal cramping, vomiting and even fever, if the infection is bad enough.

"This is more common when traveling to certain areas of the world where the risk of gastroenteritis is high," says Dr. Quigley. "This is something you should research before your trip."

Tips for preventing traveler's diarrhea if you're traveling to a risky area include:

• Only eat food that's been cooked to the appropriate temperature
• Avoid eating raw foods, particularly salads
• Only drink filtered water from a sealed container
• Avoid adding ice in your drinks
• Travel with ciprofloxacin if you have a GI condition that makes you prone to diarrhea (to take only if you experience an infection)

8. Disruption of your biological clock

When travel takes you across time zones, it can impact your circadian rhythm — your body's way of setting and timing its internal clock.

"There's diurnal variation in a lot of the body's physiological processes, colon motility included," explains Dr. Quigley. "At nighttime, our colon goes to sleep with us. In the morning, our colon wakes up and we see a big increase in activity."

But when what's 10 p.m. to your internal clock is actually 8 a.m. in your new location, colon confusion ensues. This can contribute to GI issues, namely constipation.

"Changing your internal clock by a few hours isn't a big deal, but 10, 15 hours — that's a significant change that can really disrupt your body's rhythm," says Dr. Quigley. "This can lead to irregular colon motility and contribute to constipation."

9. Forgetting to bring your medications if you have a known GI issue

It might seem obvious, but Dr. Quigley points out that forgetting to pack medication you take for an existing issue is a common way to end up with digestive problems on a trip.

"Whether it's an over-the-counter acid blocker for acid reflux, daily oral laxative for treating constipation or a prescription medication for colitis, we hear about this all the time," says Dr. Quigley. "And once you do realize you've forgotten your medication, finding a replacement isn't always straightforward."

If you're traveling to another country, trade names of products can differ, and filling prescriptions certainly isn't always a guarantee.

Dr. Quigley also points out that people prone to constipation, in particular, shouldn't be afraid to increase their meds.

"Especially if the person has a history of their constipation worsening with travel, we often recommend they prepare by taking an additional dose of laxative," says Dr. Quigley. "People are often afraid to increase their laxative dosage for fear of becoming dependent, but they needn't be reluctant to do so."

10. Being unprepared for motion sickness

Motion sickness, also sometimes called travel sickness, may not be something you think about often, but it might be important to consider when making your travel plans — especially if you don't know how you'll react to a type of travel known to cause motion sickness, like cruise ships.

"This isn't actually a digestive problem, but the symptoms can be related to the digestive system — nausea and vomiting," says Dr. Quigley.

Over-the-counter remedies can help alleviate motion sickness, but there are also strategies for preventing it if you're prone, like keeping your eyesight on the distant horizon when on a boat.