Travellers' illness is common and largely preventable, and the folk advice is a rough approximation of the evidence.
Where risk actually concentrates
Food held at unsafe temperatures and prepared with contaminated water.
Which is a narrower category than avoiding street food entirely.
Water
Drinking water, ice and washed produce.
Busy stalls
High turnover meaning food is freshly cooked.
Which is why popular street vendors are frequently safer than quiet restaurants.
Hand hygiene
Consistently the most effective single measure.
Which is easy to overlook while travelling.
What the evidence actually supports
The main risks are food that has been cooked and then held warm for a long time, raw items washed in unsafe water, and hands.
Which does not map neatly onto the usual advice to avoid street food and eat in hotels.
A vendor cooking to order in front of you, with high turnover, is frequently a lower risk than a hotel buffet that has been standing under lamps.
Water and ice
Sealed bottled water or treated water where supply is unsafe.
Which includes ice, salads and brushing teeth in higher-risk areas.
Hand hygiene
Washing or sanitising before eating.
Which is the single most effective measure.
If you become ill
Rehydration first, and medical attention for severe or prolonged symptoms.
A general note
This is general guidance rather than medical advice; travel health services provide destination-specific information.
Practical habits that work
Eat where there is a queue of locals, choose food cooked to order rather than held, be careful with raw items and ice where water quality is uncertain, and wash your hands.
Which is a short list that addresses most of the actual risk.
Avoiding all street food while eating from a hotel buffet is a common approach that gets the risk assessment backwards in many destinations.
Preparation before travelling
Travel health advice and any recommended vaccinations.
Which should be arranged weeks ahead.
Rehydration
Oral rehydration salts as the standard treatment.
Which are cheap and worth carrying.
When to seek help
Blood, high fever, severe dehydration or prolonged symptoms.
A general note
Destination-specific advice from a travel health service is the appropriate source.
What actually causes most cases
Bacterial contamination from food held at unsafe temperatures or handled without adequate hygiene, and contaminated water.
Which is a specific mechanism rather than an inherent property of unfamiliar cuisine.
Most cases are self-limiting and unpleasant rather than dangerous, and rehydration is the main treatment.
Higher-risk foods
Raw and undercooked items, unpasteurised dairy and pre-cut fruit.
Which varies by destination and by preparation.
Medication
Antimotility drugs and antibiotics having appropriate and inappropriate uses.
Which travel health professionals advise on.
Vulnerable travellers
Children, older travellers and those with conditions needing more caution.
A general note
This is general information; destination-specific medical advice should come from a travel health service.
Why the travel industry is so hard to see into
Almost every part of a holiday is sold by one company, delivered by another and regulated by a third, frequently across several countries. The traveller deals with a single price and a single confirmation, and the arrangements behind it are invisible.
That structure is not designed to confuse anyone. It exists because travel involves aviation, accommodation, ground transport, insurance and consumer protection, and no single business does all of those well. The consequence is that when something goes wrong, working out who is responsible is genuinely difficult, and the answer frequently depends on how the booking was assembled rather than on what actually happened.
The questions worth asking before booking
Who is the organiser, what protection applies if a supplier fails, what exactly is included in the price, and what happens if plans change. Four questions, all answerable at the point of booking, and between them they cover most of the situations that produce complaints afterwards.
None of this makes travel more complicated than it is. It makes visible a set of decisions that are being made whether or not the traveller notices them.
A general note
Consumer protection, aviation passenger rights, classification schemes and insurance regulation all differ substantially between countries, and change. National regulators and consumer bodies publish the applicable rules, and they are the authoritative source for anything with money or a legal position attached.
One habit worth adopting
Before paying for anything in travel, read the part of the confirmation that describes what happens if it does not go ahead. Not the terms in full, just that section.
It takes two minutes, it is where the meaningful differences between apparently similar offers actually sit, and it is the only part of the documentation that matters on the day something goes wrong.
Where to find reliable information
National tourist boards, aviation regulators and consumer protection bodies all publish material aimed at travellers rather than at the industry, and it is free, specific and rarely promoted.
It is considerably more useful than the general advice that circulates, and it has the advantage of being current for the country you are actually going to.