A day in Tijuana or a longer trip into Mexico can end with cramps, loose stools and hours close to the bathroom. Traveler's diarrhea is the most common travel-related illness, according to the CDC, which lists Mexico among the highest-risk destinations. For San Ysidro families who cross often for work, school or visits with relatives, it helps to know which cases can be handled at home, which need a clinician, and when a stool test changes the treatment plan.
Common Causes After Eating or Drinking in Mexico
Most cases come from germs in food or water. The CDC Yellow Book, the agency's clinical guide to travel medicine, reports that bacteria cause an estimated 75% to 90% of cases, led by enterotoxigenic E. coli, then Campylobacter, Shigella and Salmonella. Viruses such as norovirus cause 10% to 25%, and parasites such as Giardia about 10%, mostly in longer-term travelers.
The CDC's food and drink guidance for travelers flags the same higher-risk choices again and again: cut-up fruit, raw vegetables, fresh salsas made from raw ingredients, ice, and unpasteurized milk, cheese and yogurt. Its Mexico travel health page also names raw or undercooked beef and unpasteurized cheese as foods to avoid.
Home Care and Rehydration for Traveler's Diarrhea
Many cases clear up on their own within a week. Your main job at home is to replace lost fluid.
- Drink steadily. The CDC advises plenty of fluids and, for more serious cases, an oral rehydration solution from a pharmacy.
- For adults, MedlinePlus suggests water or sports drinks with electrolytes for mild dehydration.
- For children, the American Academy of Pediatrics recommends an electrolyte solution and advises against soda, juice and sports drinks, which have the wrong amounts of sugar and salt.
For mild cases in adults, the Yellow Book mentions over-the-counter loperamide or bismuth subsalicylate, with limits. Loperamide alone is not recommended for bloody diarrhea or diarrhea with fever. Bismuth subsalicylate is not recommended for children under 3, during pregnancy, or for people with an aspirin allergy or who take blood thinners, and it commonly turns stool black.
The Yellow Book does not recommend antibiotics for mild cases, and the CDC warns that unneeded antibiotics bring side effects, including diarrhea and C. diff infection, without helping. Holding leftover antibiotics or pills bought across the border? Talk with a clinician first, and see our guide to buying medicine in Tijuana.
Red Flags: Blood, High Fever and Dehydration
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) advises talking with a doctor right away for:
- Stools that are black and tarry or contain red blood or pus
- Severe pain in the belly or rectum
- Frequent vomiting
- A change in mental state, such as irritability or lack of energy
- In adults: diarrhea lasting more than 2 days, a high fever, or six or more loose stools a day
- Dehydration: extreme thirst, urinating less than usual, dark urine, or feeling dizzy or lightheaded
When to Go to the ER or Call 911
Severe dehydration can require hospital care. MedlinePlus lists signs such as passing no urine or very dark amber urine, dry and shriveled skin, confusion, a rapid heartbeat and rapid breathing. Call 911 if a dehydrated person loses consciousness, becomes confused or has a seizure, has a fever over 102°F, or gets worse despite treatment. If bloody stools or severe belly pain come with any of these signs, call 911. Unsure which setting fits? Read our guide to urgent care vs the emergency room.
When a Stool Test Helps Pick the Right Treatment
A lab test is most useful when the illness is severe, bloody or slow to clear. The CDC advises that if severe diarrhea starts soon after you return from a trip, you should see a doctor and ask about stool tests to find out which antibiotic will work.
According to MedlinePlus, a stool (fecal) culture looks for organisms in the stool that cause digestive illness. It is often ordered for severe, bloody diarrhea with fever, or diarrhea that does not go away or keeps coming back. The Yellow Book adds that parasites such as Giardia are more likely to be found when diarrhea lasts longer than 2 weeks, and that this kind of diarrhea can persist for weeks to months without treatment.
Causes differ. The CDC notes that antibiotics do not work on viruses, and the Yellow Book describes lingering bowel symptoms after the infection is gone, called post-infectious irritable bowel syndrome. If a sample is needed, MedlinePlus advises keeping it free of urine, water and toilet tissue and returning it to the lab promptly. Learn more in our guide to lab testing at urgent care.
Kids, Seniors and Dehydration Risk
The Yellow Book stresses that replacing fluids matters most for young children, older adults and adults with chronic illness. The NIDDK adds that people who are pregnant, over 65, taking antibiotics or living with a weakened immune system are more likely to have problems from diarrhea and should stay in touch with their doctor. MedlinePlus notes that older adults and people with diabetes are especially vulnerable to dehydration.
For children, the NIDDK advises seeing a doctor if diarrhea lasts more than a day, for any fever in an infant, or for no wet diapers in 3 hours or more, no tears when crying or a sunken soft spot. The American Academy of Pediatrics lists severe dehydration signs that need a call to the pediatrician right away: a child who is very fussy or excessively sleepy, sunken eyes, cool or discolored hands and feet, or urinating only once or twice a day. Ask a clinician before giving a child any anti-diarrhea medicine.
Food and Water Tips for Frequent Crossers
When crossing is part of your routine, the CDC's food and drink guidance works best as a set of habits:
- Wash hands with soap and water before eating and before preparing food, or use a sanitizer with at least 60% alcohol.
- Choose factory-sealed bottles or cans. Carbonation signals a factory seal.
- Skip ice where access to clean water is limited.
- Eat hot food hot. Germs multiply quickly between 40 and 140 degrees F.
- Pass on cut-up fruit, raw vegetables and fresh salsas.
- Avoid unpasteurized dairy, especially during pregnancy or with a weakened immune system.
- Know that the CDC advises against food from street vendors.
The Yellow Book notes that even people who follow food rules closely can still get sick, so keep oral rehydration packets at home.
Walk-In Care and Lab Testing in San Ysidro
Palm Urgent Care, San Ysidro is at 601 E San Ysidro Blvd #170, San Ysidro, CA 92173, serving the border community near the San Ysidro Port of Entry, from Spanish-speaking families to cross-border workers. The clinic offers walk-in urgent care and lab testing, so a clinician can examine you, check for dehydration and decide whether a stool test is needed. Check current hours and directions on the San Ysidro location page.
Frequently Asked Questions
How long does traveler's diarrhea last?
The CDC Yellow Book reports that untreated bacterial diarrhea usually lasts 3 to 7 days and viral diarrhea 2 to 3 days, while parasites can cause symptoms for weeks. See a clinician if an adult is not better after 2 days or a child after 1 day.
Do I need a stool test for diarrhea after a trip to Mexico?
Not always. The CDC advises seeing a doctor and asking about stool tests if severe diarrhea starts soon after you return. Testing is also common for bloody diarrhea with fever, diarrhea that keeps coming back, or diarrhea lasting longer than 2 weeks.
What should I drink when I have diarrhea after traveling?
Drink plenty of fluids, and use an oral rehydration solution for more serious cases. For children, the AAP recommends an electrolyte solution instead of soda, juice or sports drinks.
When is diarrhea an emergency?
Call 911 for fainting, confusion, a seizure, a fever over 102°F with dehydration, or symptoms that keep getting worse despite treatment. Black or bloody stools, severe belly pain and frequent vomiting need a doctor right away.
Still running to the bathroom days after a trip south? Visit Palm Urgent Care, San Ysidro for walk-in care for traveler's diarrhea, close to the border.
This article is for general information and is not a substitute for medical advice from a licensed clinician.