- Most travellers' diarrhoea settles on its own; the main job is replacing lost fluid, ideally with oral rehydration solution (ORS).
- The US CDC advises against anti-diarrhoea medicines such as loperamide on their own if there is blood in the stool or a fever.
- See a doctor for blood in the stool, a high fever, signs of dehydration, vomiting that stops you keeping fluids down, or symptoms that are not improving after a few days.
- Babies, young children, older people, pregnant women and people with long-term conditions dehydrate faster and need care sooner.
- Call 1669 for anyone who is confused, very drowsy, collapses or cannot be roused.
What usually happens
Stomach upsets are among the most common health problems for visitors to Thailand. The World Health Organization describes foodborne disease as illness caused by bacteria, viruses, parasites or chemicals in food or water, and lists diarrhoea, vomiting and stomach cramps among the usual symptoms. Symptoms can start within hours of eating contaminated food or several days later, depending on the cause, so the last meal is not always the culprit.
In most healthy adults the illness is unpleasant but short. The NHS notes that food poisoning usually gets better on its own within a week, and often within a few days. The risk is less the infection itself than the fluid and salts lost through vomiting and diarrhoea, especially in heat, which is why rehydration matters more than anything else in the first day or two.
Looking after yourself at your accommodation
Drink little and often. The CDC's guidance on travellers' diarrhoea says that for significant fluid loss, replacement is best done with oral rehydration solution (ORS), and that mild cases can be managed with other safe drinks. Pharmacies in Thailand sell ORS sachets; mix them exactly as the packet says, using bottled or boiled water. If you are vomiting, small sips every few minutes are more likely to stay down than a full glass.
Rest, stay out of the heat and eat when you feel able. There is no need to force food, but plain, easily digested meals are a sensible way back. Alcohol makes dehydration worse and is best avoided until you have recovered.
Be careful with medicines. The CDC states that anti-motility drugs such as loperamide are not recommended on their own for people with bloody diarrhoea or with diarrhoea and fever, because these can be signs of an invasive infection that needs medical assessment. It also notes that loperamide is rarely given to children under six. Do not take antibiotics left over from a previous illness or bought without advice; ask a pharmacist or doctor, who can judge whether an antibiotic is appropriate.
When to see a doctor
Go to a clinic or hospital the same day if you have blood or mucus in your stool, a high fever, severe or worsening abdominal pain, or vomiting that means you cannot keep any fluids down. See a doctor, too, if symptoms are not improving after a few days, or if you have a long-term condition such as diabetes, kidney disease or a weakened immune system.
Watch for dehydration: passing little or no urine, very dark urine, dizziness when standing, a dry mouth and unusual tiredness. In babies and young children, the CDC notes that dehydration happens faster, so oral rehydration should start early; a child who is drowsy, floppy, has a sunken soft spot on the head, few wet nappies or is not drinking needs to be seen promptly.
A doctor may test a stool sample, check your blood salts and give fluids through a drip if you are dehydrated. Hospital outpatient departments and many clinics can see you without an appointment. Bring your passport and insurance details, since even a short visit is usually charged.
When it is an emergency
Call 1669, Thailand's free medical emergency number, if someone is confused, very drowsy or difficult to wake, collapses, has a seizure, or has signs of severe dehydration with a rapid heartbeat and cold, clammy skin. Also call for help if vomiting follows a head injury, or if there is vomiting with a severe headache and stiff neck, since these are not food poisoning.
Some symptoms that look like a stomach bug can be something else. A fever with vomiting in Thailand may be dengue or another infection; our guide to dengue and rabies explains the warning signs. Severe abdominal pain that settles in one place, particularly the lower right side, needs urgent assessment.
This guide summarises published public-health guidance. It is not a substitute for first-aid training or for the instructions of the 1669 call handler or a doctor; if in doubt, call 1669.
Lowering your risk
The WHO's food safety advice comes down to a few habits: keep hands and surfaces clean, separate raw and cooked food, cook food thoroughly, keep it at safe temperatures and use safe water and raw materials. For a traveller, that means choosing food that is freshly cooked and served hot, peeling fruit yourself, drinking sealed bottled water or water from a trusted filtered source, and washing or sanitising your hands before eating.
Busy stalls with a quick turnover are often a better bet than food that has been sitting out. Be more cautious with raw or lightly cooked seafood, salads washed in tap water, and ice of unknown origin, particularly if you are pregnant, older or have a weakened immune system.
If you have vomiting or diarrhoea
- Sip oral rehydration solution little and often, mixed with safe water exactly as the packet says.
- Do not take loperamide on its own if there is blood in the stool or a fever.
- See a doctor for blood in the stool, high fever, severe pain or if you cannot keep fluids down.
- Get a child, older person or pregnant woman seen sooner rather than later.
- Call 1669 for confusion, collapse, a seizure or severe dehydration.
- Keep receipts and a copy of any medical report for your insurer.
Frequently asked questions
How long does food poisoning usually last?
The NHS says food poisoning usually gets better on its own within a week, often within a few days. See a doctor if symptoms are severe, include blood in the stool or a high fever, or are not improving.
Can I buy oral rehydration salts in Thailand?
Yes, pharmacies sell oral rehydration salt sachets. Mix them with bottled or boiled water exactly as the instructions say.
Should I take loperamide for travellers' diarrhoea?
The US CDC advises against using anti-motility medicines such as loperamide on their own if you have bloody diarrhoea or diarrhoea with fever. Ask a pharmacist or doctor if you are unsure, and be cautious with children.
Do I need antibiotics for food poisoning?
Most cases do not need antibiotics. A doctor can decide whether one is appropriate, for example for severe or bloody diarrhoea. Avoid taking leftover or unprescribed antibiotics.
When should I call an ambulance for food poisoning?
Call 1669 if someone is confused, very drowsy, collapses, has a seizure or shows signs of severe dehydration such as a racing heart and cold, clammy skin.
