What is it?

It's defined as three or more loose stools in 24 hours with or without cramps, nausea, fever or vomiting. More serious variations include blood in the stool. It should usually get better within two to three days and you should be over it within a week.

How do your get it?

Eating or drinking food or water contaminated by someone's faeces, which is carrying bugs. It is more common in countries where disposing of sewage is poorly organised, and where kitchen and toilet hygiene are poor and water may be contaminated. It is often caused by bacteria (around 85% of cases) such as E coli, but can be caused by viruses and protozoa (a one-celled parasite). You may be more at risk if you take tablets that block acid production, if you have an inflammatory bowel condition or diabetes.

How can I treat it?

You will lose lots of fluids and minerals and salts so you must replace them. Children are at risk of dehydration and you may need to get a doctor to assess them quickly. You should drink flat, decaffeinated soft drinks, or sports drinks or fruit juices. Don't just drink water. You can buy solutions with minerals – eg Dioralyte – from the chemist. After a couple of days, try eating salted crisps or plain biscuits or dry bread and build up to dairy products after a few days.

You can take loperamide, which slows the motility of your gut and so reduces diarrhoea quite dramatically sometimes. But do not take it if you have a fever or blood in your stools and not more than for a day or two. Children shouldn't take it. If the infection is caused by bacteria you may need to take antibiotics from a doctor.

How can I prevent it?

Avoid street vendors. Stick to well-cooked meat and vegetables served hot. Avoid shellfish, or any fish really, undercooked meat, and any food (especially if it has a dairy or meat component) that is served in a buffet at room temperature. Don't eat any food that has been heavily prepared by human hands and is uncooked, eg salads. With fruit, if you can't peel it, don't eat it. Say no to fruit platters even in posh hotels. Be careful of water in countries such as India, anywhere in Africa or South America: if you need to drink local water, boil it for five minutes first. No water means no ice cubes and no teeth brushing (use bottled water). Drink tea and coffee and make sure they come to you very hot. Wash your hands before you eat.

When should I see my doctor?

If you have symptoms for more than three days, if they are severe or if there is blood in your stools. If you have signs of dehydration (feel dizzy, dry, disorientated and pass less urine), or if you have a high fever. If you have an underlying health problem such as inflammatory bowel disease, diabetes or any problems with your immune system you should see a doctor promptly.