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.
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 12-36 hours) after eating the infected food and last for two to five days.
- Campylobacter: gastro symptoms appear in two to five days, and last for two to ten days.
- Listeria: gastro or flu-like symptoms usually appear within three 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 one or two days (norovirus) or up to six days (rotavirus).
- E. coli: gastro symptoms usually appear in three to four days and last about a week.
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.
Food poisoning treatment
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.
You should also 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, replenishing fluids and electrolytes (this may be helped by obtaining oral rehydration solutions available in pharmacies) 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.
If your child has food poisoning, see your doctor or call healthdirect on 1800 022 222.
Last reviewed: February 2017