What’s difference between food poisoning, gastro? 

Gastroenteritis and food poisoning both cause symptoms like diarrhoea, vomiting, and abdominal pain, but differ in cause and onset. Gastro is typically a gut infection from viruses or bacteria, often spread via contaminated surfaces or people. Food poisoning occurs from eating food tainted with toxins, chemicals, or microbes

If you’ve got a dodgy tummy, diarrhoea and have been vomiting, it’s easy to blame a “tummy bug” or “off food.” But which is it? Gastro or food poisoning? What’s the difference anyway?

What’s gastroenteritis?

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Gastroenteritis, or gastro for short, is a gut infection caused by a virus, bacterium or other microbe. The gut is teeming with cells including healthy microbes and the cells lining the gut. But when viruses, bacteria and other microbes start to invade your gut, they colonise, build up in large numbers and eventually cause the cells lining the gut to inflame.

The “-itis” at the end of gastroenteritis means inflammation. Gastroenteritis is extremely common.

So where do these gastro-causing microbes come from? Eating contaminated food is often the source. However you can acquire these microbes in other ways. For example, if you touch a surface where someone sick from viral gastroenteritis had vomited on, that virus could transfer to your hands. And if your hands touched your mouth, you in turn could contract viral gastroenteritis.

What’s food poisoning?

Food poisoning refers to getting sick from eating food contaminated with chemicals, microbes or toxins. For example if you ate food contaminated with insecticides or methyl alcohol (methanol) that would count as food poisoning.

If you ate puffer fish or poisonous mushrooms that would count too. But food poisoning doesn’t include the effects of eating a food you’re allergic to. The vast majority of food poisonings are as a result of food contaminated by microbes and their toxins. When you eat or drink them it’s like a missile strike. The toxins in particular can rapidly cause inflammation and damage the lining of the gut.

To add to the confusion, food poisoning is often referred to as foodborne gastroenteritis.

How can we tell the two apart?

Both gastroenteritis and food poisoning have symptoms such as diarrhoea, vomiting, nausea, abdominal cramps, fever and headaches. But these symptoms can come on in different ways.

Viral gastroenteritis, such as with norovirus, usually causes symptoms 24-48 hours after exposure, which can last for one to two days.

But food poisoning after eating microbial toxins can come on very quickly. For example, toxins from the bacterium Staphylococcus aureus can cause symptoms within 30 minutes of eating contaminated food, such as undercooked meat. Fortunately, symptoms usually get better within 24 hours.

Symptoms don’t always come on so quickly in all cases of bacterial food poisoning. For example, it can take as long as 70 days between exposure to Listeria and symptoms occurring, although, on average it’s about three weeks. This long incubation period can make it difficult to work out if a particular food is responsible for someone getting sick. As a general guide food poisoning occurs quite quickly (within hours of eating contaminated food) while gastroenteritis can take a day or more after eating to get sick. But there is no hard and fast rule.