Oxal and Floratil

No matter how careful you are about what you eat and drink here in Mexico, you will get some sort of parasite-based gut rot.  Often, a doctor will not diagnose and treat gut-rot until a stool sample comes back positive for an organism, which unfortunately often requires multiple samples be taken because of the life cycle of microscopic organisms.  This can take weeks of collecting your own noxious diarrhea.  Instead, a person showing symptoms can go to the pharmacy and get a full-spectrum parasiticide like Oxal.

Oxal kills amoeba (dysentery), protozoa (giardia), nematodes (roundworms), and cestodes (tapeworms) -- basically, everything but viruses and bacteria (including tissue-parasites like trichinosis).  It should not be taken by children under 2 or pregnant or breatfeeding women.  Men who take it should avoid possibly conceiving children for up to one month afterwards.

While you're at the pharmacy, pick up some Floratil -- a natural gut flora supplement.  It is used both in the treatment and prevention of diarrhea.  Because it is some of the same stuff that you already should have in your system, anyone in most any condition can take it, including children.  There is a pediatric version, but it is literally the exact same powder as is in the capsules (so sayeth the pharmacist).  Also, you can't overdose on the stuff.

Good luck!