Attention all you travellers out there heading to San Cristobal de Las Casas – don’t be naive, I was. The rumours are true; the tap water is contaminated, unsafe and will make you seriously sick. You can’t shower with your mouth open, let alone be drinking it.
San Cristóbal de las Casas is such a beautiful, lush mountain town where you’d think the water would be clean and plentiful, but that isn’t the case. San Cris, and the region in general, has a reputation internationally as the town where residents drink 2 litres of Coca-Cola daily.
Locals and businesses must pay for 20L water containers, which are costly. In a place where fizzy drinks are more available than drinkable water, it’s no wonder that the diabetes rates in Mexico are sky-high.
This post covers how unsafe the water is in San Cristóbal de Las Casas, how to avoid getting sick, and what to do if you become unwell (I went through it, so you don’t have to!).
Why is the water so contaminated in San Cristóbal?
“Coca-Cola pays this money to the federal government, not the local government…while the infrastructure that serves the residents of San Cristóbal is literally crumbling.”Laura Mebert
A large part of it comes down to Coca-Cola. On the edge of town, you’ll find a big Coca-Cola plant with a permit to extract more than 300,000 gallons of water per day. The permit was signed decades ago when the town was less touristy and smaller in population and definitely made on the back of a dodgy deal.
Due to the rise in tourism, the town doesn’t have the infrastructure and proper waste management to deal with the demand. The lack of waste management means that the city’s raw sewage is flowing into local waterways. That’s why I wouldn’t recommend swimming around San Cristóbal, especially in places like Arcotete Park. It’s just not safe.
An interesting YouTube documentary reports this crisis with Coca-Cola and the water. Check it out here: Mexico’s Deadly Coca-Cola Addiction.
How sick can you get from the water in San Cristóbal de las Casas?
From my experience: very sick.
I stayed in San Cristóbal for two months in 2022 and then recently returned for one month in January 2025, and the situation remains the same.
The first time in January 2022, I felt great one night, and the next day, I woke up and started feeling extremely weak and unable to stomach any food or liquids. Only after three days of feeling really bad, I dragged myself to the lab to get tested, and it came back positive with two kinds of parasites and salmonella. The doctor prescribed me a 5-day course of antibiotics, and for sure, it worked, but it wasn’t until I left San Cristóbal 6 weeks later that I felt healthy again.
The second time in January 2025, the moment I started to feel nauseous, I went straight to the lab to do a stool sample. The results came back positive with two kinds of parasites (dammit!). I went to the doctor, got prescribed anti-parasite medication and electrolytes. After a week, no improvement. I went back to the lab to do a full blood test, and it showed I had an infection. Went back to the doctor and got prescribed antibiotics. This time it worked, thankfully.
How do I avoid getting sick from the water in San Cristóbal?
I got sick twice. The first time, I was naíve about the situation; the second time, I think I became complacent and not careful enough.
I’m not only saying you shouldn’t drink the water, but you should also not:
- Open your mouth in the shower
- Wash any fresh produce with tap water (only filtered).
- Brush your teeth with tap water.
- Forget to wipe every drop of water off your glasses and plates when you use them.
- Drink any iced drinks.
- Forget to wipe all the water off your hands when you wash your hands (sounds extreme, I know, but it’s necessary.)
- Eat any uncooked veggies or salad in restaurants.
What to do if you get sick from the water in San Cristóbal?
Here is what you need to do if you feel sick in San Cristóbal de las Casas and suspect it’s water contamination:
- Act fast: the faster you react, the sooner you’ll recover and the less severe it’ll be.
- Go to the lab: As soon as you feel symptoms of tiredness, belly aches, or diarrhoea, walk into any of the labs dotted around San Cris. To find your closest one, type into Google Maps ‘laboratorio de análisis clinicos’.
- Test your stool and blood: I went for both; the total cost was MXN200.
- Results will be delivered by WhatsApp a few hours later.
- If your results are positive, go see the doctor here. First, you’ll need to go to the pharmacy next door to pay for a consultation (it costs MXN50). The doctor will then look at your results and give you a prescription.
- Go back to the same pharmacy to pick up anything you need.
I hope I didn’t scare you off by heading to San Cristóbal de Las Casas. It’s one of my favourite towns in Mexico. Just know how unsafe the water is and try your best to stick to my advice above!