Can infecting children with stomach ulcer bacteria stop allergies?

DR MICHAEL MOSLEY: Can infecting children with stomach ulcer bacteria really stop allergies in their tracks?

Every June I start to sneeze and itch and get watery eyes and a stuffy nose. Along with ten million other Britons, I am prone to hay fever. I am particularly allergic to grass pollen, and the months of June and July are peak season.

Hay fever symptoms are caused by the immune system mistakenly treating pollen as a potentially dangerous invader, and mounting an aggressive response.

Such allergies are not only extremely common, but also on the increase. Why? A plausible theory is that this is happening because these days children are not exposed to enough of the right sort of bacteria.

Hay fever symptoms are caused by the immune system mistakenly treating pollen as a potentially dangerous invader, and mounting an aggressive response (stock image)

So would deliberately infecting children with potentially dangerous microbes help to stop that happening? It’s an idea being actively pursued by one of my all-time scientific heroes, Australian Nobel Prize winner Professor Barry Marshall.

I first came across Barry in 1994 when I made a film about work he was doing on a little-known bacterium called Helicobacter pylori, or H. pylori.

He and a colleague, Dr Robin Warren, had become convinced that infection with H. pylori, a bug they were the first to identify and grow, was responsible not only for most cases of stomach ulcers but also many incidences of stomach cancer.

Australian Nobel Prize winner Professor Barry Marshall (pictured) is behind the idea that deliberately infecting children with potentially dangerous microbes could help with allergies

At that time it was widely believed nothing could live in our extremely acidic stomach. So to make his point, Barry deliberately infected himself by swallowing a beaker of these dangerous microbes.

He proceeded to develop early signs of a stomach ulcer, which he then cured with antibiotics.

As well as this slightly crazy self-experiment, Barry and Robin carried out a number of clinical trials showing that H. pylori eradication was an effective way of treating stomach ulcers. They went on to win the Nobel Prize for Medicine for their discovery.

So, I was surprised to hear from Barry that he was now working on experiments to see if deliberately infecting children with an inactive or weakened form of H. pylori would actually benefit them, by helping to prevent allergies later in life.


About one person in four in the UK has an allergy. Along with hay fever, or pollen allergy, people commonly have reactions to dust mites and certain foods.

Most allergies are on the rise, along with other diseases linked to an over-active immune system such as asthma and eczema, and digestive illnesses from coeliac to Crohn’s. The reason for this isn’t fully understood.

As regular readers will know, one of my big areas of interest is the microbiome – the three or so pounds of microbes, including bacteria, fungi, viruses and other organisms, that live in our digestive tract.

DR MICHAEL MOSLEY: As regular readers will know, one of my big areas of interest is the microbiome – the three or so pounds of microbes, including bacteria, fungi, viruses and other organisms, that live in our digestive tract

Many are essential for our wellbeing, and our immune system has evolved, over millions of years, to live in harmony with this mini zoo.

So although they are, essentially, foreign bodies living inside us, it doesn’t attack them as it would an infection. In fact, it is believed that certain microbes ‘teach’ the immune system how to behave, keeping it in check.

Unfortunately, over the past few hundred years, our microbiome has undergone a dramatic change. There are fewer types of bacteria down there than there used to be.

This is partly because of the over-use of antibiotics, which kill off infections but also destroy ‘good’ bacteria.

It’s also possibly because many processed foods now contain additives that prolong their shelf life but which are toxic to gut flora.

And the absence of certain microbes may cause the immune system to behave like a delinquent teenager that has never had proper supervision – it goes haywire, attacking things, like pollen, that are harmless.

Ask Dr Mosley: Your questions answered 

I was surprised to see you recommend full-fat yogurt in your diets. I have high cholesterol, which I try to control with my food choices. Is fat-free yogurt equally effective for weight loss?

The main reason I eat full-fat Greek yogurt is that I enjoy the taste and flavour. 

I also find it fills me up far more effectively than low-fat variants, particularly if I add a small handful of walnuts. 

There are plenty of studies which suggest that people who eat full-fat yogurt tend to be slimmer than those who go for low-fat options, and plain yogurt is an important component of the Mediterranean diet (low-fat yogurt plays no part in traditional ways of eating). 

Yogurt contains lots of important vitamins and minerals, as well as being a great source of probiotics (living bacteria). But if you prefer zero-fat yogurt, that’s fine. 

You should check the side of the pack to make sure it contains live cultures and doesn’t have added thickeners and sweeteners.


So, if the immune system is misbehaving due to lack of bacteria, why not try to put some of them back? That, in a nutshell, is the basis of Barry’s current research.

And one of the bugs he’s thinking of reintroducing is the one he has spent so long trying to eradicate: H. pylori.

Helicobacter has colonised our digestive system for hundreds of thousands of years. Spread through contaminated food and water, most people are infected during childhood.

Although some go on to develop ulcers and stomach cancer, most people seem to be able to tolerate the bacteria perfectly well. The bug is actually no longer common in Western countries, thanks to our impressive standard of hygiene, and you might be thinking: ‘Good riddance!’ But as H. pylori infections have dwindled, allergies have risen.

A US study looking at more than 7,600 people found those who did have H. pylori in their system – but had no symptoms – were almost 50 per cent less likely to develop allergies or asthma.

Scientists remain cautious about bringing this bacteria back, as there is no predicting when it could go rogue and cause serious health consequences.

But Barry and his team are testing an inactive form of the microbe that would, in theory, teach our immune system to behave – without the disadvantages of the live bacteria.

They hope to develop an edible substance that can be given to children at risk of allergies to stop the sensitivities from developing.

Because gut bacteria are valuable, we should take care of them. This means avoiding antibiotics, if you can. Your microbiome can take months to bounce back after a course of medication.

And eat as diverse a range of fruit and vegetables as you can, as your microbiome loves fibre.

Also, do get your hands dirty, preferably by gardening. This connects you with the trillions of bacteria that live in the soil, and it is also a great form of exercise.

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