Is it Food Poisoning or a Stomach Bug?

I am often asked the difference between food poisoning and gastroenteritis, or diarrhoea and vomiting caused by a bug. The truth is that in many cases the two terms can be used interchangeably.

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And unfortunately, it's difficult to tell clinically whether your symptoms are from eating contaminated food or because someone's passed on a nasty bug to you.

Though it's worth noting that diarrhoea illnesses are often caused by viruses rather than bacteria and are usually what we call "self limiting", in other words, they can be managed at home without the need to see a doctor. 

But how do you know when that isn't the case, and what if you suspect your illness is related to food you have eaten?

Food poisoning is caused by eating contaminated food and the symptoms may be caused by a bug or by toxins produced by the bug. We can sometimes predict which bug is likely to be to blame by the time frame. Diarrhoea due to staphylococcus aureus for example, develops within one to six hours of eating contaminated food, whilst food poisoning from salmonella, E Coli or norovirus is more likely to develop a day or two after eating contaminated food and may even occur several weeks later.

The only real way of knowing which bug is to blame though is to send a sample to the laboratory for assessment and as most cases of diarrhoea and vomiting settle within a couple of days, we don't always do this.

Food can become contaminated at any point in its preparation. Common causes include not cooking meat thoroughly or not reheating foods previously cooked foods, leaving food out in warm temperatures or next to other foods which are contaminated, and not washing hands properly before preparing food.

Diarrhoea serves a purpose

If we ingest harmful bacteria, diarrhoea is our body's way of getting rid of that bug and that is why we ask patients to keep well hydrated by drinking plenty of fluids and we don't give medication to stop the diarrhoea in the first 24 hours. It is important that we allow our system to get rid of the infection. If you are suffering severe dehydration as a result of sickness, rehydration products such as Dioralyte (RRP £3.79) can aid recovery.

But not all bacteria in our gut are bad. In fact we all have two kilos of "good" bacteria living in our intestines and they are vital to our health. They help us digest our food. When we develop diarrhoea, we lose those some of those good bacteria along with the harmful ones and that means that even after the infection has cleared, we struggle to digest our food properly and diarrhoea can persist. It's at this stage that we encourage patients to use anti-diarrhoeal medicines and I also recommend a daily probiotic (RRP £14.99) to top up our "good" bacteria.

When to worry

You should see your doctor if diarrhoea persists for more than a few days and certainly if there is blood in the motions. A high fever or severe tummy pains should also be checked out and if you have reason to believe that your symptoms are related to eating contaminated food from a restaurant or other food outlet, your GP will want to send a sample to the laboratory. If food poisoning is confirmed, he or she will report the results to the local environmental health department for further investigation to prevent others being infected.

Am I contagious?

Even if it's probably food poisoning, it's best to assume that you are infectious for as long as you have symptoms and take extra care with hand washing after using the toilet and before preparing or eating food and should avoid preparing food for others wherever possible until the diarrhoea has settled.

AUTHOR 

By Dr Dawn Harper