What is food poisoning?

Food poisoning is caused by bacteria, viruses or toxins in the food we eat. Some of these toxins are found naturally in foods, while some have accumulated in the environment.

If you have food poisoning you’ll probably have gastroenteritis symptoms such as abdominal cramps, diarrhoea or vomiting, or flu-like symptoms. Food poisoning can also cause serious long-term problems like kidney failure. Occasionally people die from food poisoning.

Some wild mushrooms, including the death cap, are extremely poisonous. You should not eat wild-harvested mushrooms unless they have been definitely identified as safe. Seek immediate medical treatment If you think you may have eaten poisonous mushrooms.

Large fish, such as shark, swordfish and marlin, may accumulate relatively high levels of mercury. You should limit your consumption of these fish, especially if you are a child, are pregnant or planning pregnancy.

What are the symptoms and causes of food poisoning?

You may be sick with food poisoning but not know what food caused it or even that you have it. Different bacteria and viruses can have different effects:

• Salmonella: gastro and flu-like symptoms can appear between 8 and 72 hours (usually 12 to 36 hours) after eating the infected food and last for 2 to 5 days.
• Campylobacter: gastro symptoms appear in 2 to 5 days, and last for 2 to 10 days.
• Listeria: gastro or flu-like symptoms usually appear within 3 weeks, but can take up to 70 days.
• Norovirus or rotavirus: severe gastro or flu-like symptoms usually begin 24 to 48 hours after exposure and last 1 or 2 days (norovirus) or up to 6 days (rotavirus).
• E. coli: gastro symptoms usually appear in 3 to 4 days and last about 1 week.

Food needs to be stored, handled and cooked carefully and at temperatures that avoid the spread and growth of bacteria that can make you sick. Read about preparing food safely.

What are the high-risk groups for food poisoning?

If you’re pregnant, elderly or very young, or your immune system is weak through illness or drugs, you’re at greater risk of food poisoning and possibly serious complications.

If you’re pregnant, listeria can cause you to miscarry, even if you don’t know you’ve been infected. If you notice symptoms — usually like a mild flu but also diarrhoea, vomiting and nausea — contact your doctor immediately.

Read more about how to avoid listeria on the Pregnancy, Birth and Baby website.

How is food poisoning treated?

Most people don’t need medical help for food poisoning, as their symptoms are not severe and don’t last long. However, people in high-risk groups (such as babies and elderly people) should see a doctor early on, to make sure they don’t get dehydrated.

For children, see your GP or call healthdirect on 1800 022 222 if your child has diarrhoea that lasts for more than a few days or has bloody diarrhoea.

Take your child to the emergency department immediately if:

• your child has symptoms of food poisoning and is less than 1 year old
• your child has severe stomach pain and vomiting and can’t keep fluid down
• your child isn’t drinking and has signs of dehydration, including little or no wee, weight loss, tiredness and extreme thirst
• you’re worried about your child being extremely unwell

For adults, seek medical advice if:

• you still have symptoms after 3 days, or your symptoms are very severe
• you still can’t keep any fluids down, more than 24 hours after getting sick
• there is blood or mucus in your vomit or diarrhoea

For a mild case of food poisoning, you may try sucking ice chips, replacing lost fluids and electrolytes (you can buy an oral rehydration solution from your pharmacy) and easing back into your normal diet and routine when you feel ready. Antibiotics may help with some bacterial types of food poisoning, but are usually not needed.