Many travelers in Chiapas  get sunburned unwittingly, especially in highland areas like San Cristóbal  where the sun can be intense even while the temperature remains fairly cool. Use a billed hat, as well as waterproof and sweatproof sunscreen with a high SPF. Remember that redness from a sunburn takes several hours to appear—that is, you can be sunburned long before you look sunburned.
If you do get sunburned, treat it like any other burn by running cool water over it as long and as often as you can. Do not expose your skin to more sun. Re-burning the skin can result in painful blisters that can easily become infected. There are a number of products designed to relieve sunburns, most with aloe extracts. Be sure to drink plenty of water to keep your skin hydrated.
Heat exhaustion and heat stroke sometimes strike at archaeological ruins, where travelers can spend hours climbing and walking in the open sun, often without drinking enough water; it’s also a concern in hot humid areas like Tuxtla Gutiérrez  and the Pacific coast. The symptoms of heat exhaustion are cool moist skin, profuse sweating, headache, fatigue, and drowsiness. You should get out of the sun, remove any tight or restrictive clothing, and sip a sports drink such as Gatorade. Cool compresses and raising your feet and legs helps too.
Heat exhaustion is not the same as heat stroke, which is distinguished by a high body temperature, a rapid pulse, and sometimes delirium or even unconsciousness. It is an extremely serious, potentially fatal condition and victims should be taken to the hospital immediately. In the meantime, wrap the victim in wet sheets, massage the arms and legs to increase circulation, and do not administer large amounts of liquids. Never give liquids if the victim is unconscious.
Diarrhea is not an illness in itself, but your body’s attempt to get rid of something bad in a hurry; that something can be any one of a number of strains of bacteria, parasites, or amoebae that are often passed from contaminated water. No fun, it is usually accompanied by cramping, dehydration, fever, and of course, frequent trips to the bathroom.
If you get diarrhea, it should pass in a day or two. Anti-diarrheals such as Lomotil and Imodium A-D will plug you up but don’t cure you—use them only if you can’t be near a bathroom. The malaise you feel from diarrhea typically is from dehydration, not the actual infection, so be sure to drink plenty of fluids—a sports drink such as Gatorade is best. If it’s especially bad, ask at your hotel for the nearest laboratorio (laboratory or clinic), where the staff can analyze a stool sample for around US$5 and tell you if you have a parasitic infection or a virus. If it’s a common infection, the lab technician will tell you what medicine to take. Be aware that medicines for stomach infection are seriously potent, killing not only the bad stuff but the good stuff as well; they cure you but leave you vulnerable to another infection. Avoid alcohol and spicy foods for several days afterward.
A few tips for avoiding stomach problems include:
Only drink bottled water. Avoid using tap water even for brushing your teeth.
Avoid raw fruits or vegetables that you haven’t disinfected and cut yourself. Lettuce is particularly dangerous since water is easily trapped in the leaves. Also, as tasty as they look, avoid the bags of sliced fruit sold from street carts.
Order your meat dishes well done, even if it’s an upscale restaurant. If you’ve been to a market, you’ll see that meat is handled very differently here.
Insects are not of particular concern in Chiapas , certainly not like they are in other parts of the tropics. Mosquitoes are common, but are not known to carry malaria. Dengue fever, also transmitted by mosquitoes, is somewhat more common, but still rare. Certain destinations are more likely to be buggy, like forested archaeological zones, coastal bird-watching areas, and coffee-growing zones; travelers definitely should bring and use insect repellent there, if only for extra comfort.
Contrary to public perceptions, Chiapas  is a very safe and tranquil place. The Zapatista uprising occurred more than 15 years ago—15 years!—and certainly should not dissuade would-be visitors from coming. The drug-related violence plaguing Mexico, and widely reported in the international media, occurs primarily in the northern states, and in any case rarely involves tourists or other civilians. (That said, you should avoid the far eastern corner of Chiapas, along the Guatemala border, due to the presence of drug trafficking.)
Illicit drugs are relatively easy to obtain in Palenque  and San Cristóbal , but bear in mind that drug crimes, including simple possession, are prosecuted vigorously in Mexico and your country’s embassy can do little or nothing to help you.
In all areas, common-sense precautions are always recommended, such as taking a taxi at night instead of walking (especially if you’ve been drinking) and avoiding flashing your money and valuables, or leaving them unattended on the beach or elsewhere. Utilize the safety deposit box in your hotel room, if one is available; if you rent a car, get one with a trunk so your bags will not be visible through the window, and avoid driving on highways after dark.