What do microbes, obesity and climate change have to do with allergy and hayfever? 

One in three people in the UK are thought to suffer from an allergy, whether it’s to grass pollen, latex, peanuts, pets – the list goes on. The latest surveys show that rates of allergy are continuing to rise and allergy is predicted to affect more than 50 per cent of Europeans by 2021.

But the question that has been perplexing experts for some time now is: what is it about modern living that is making allergy not just common, but increasingly so? About 21 million adults in the UK suffer from at least one allergy, according to the charity Allergy UK, and there’s growing evidence to suggest that it’s the microbes that live on us and in us that are partly to blame. 

Unravelling the mystery

The “hygiene hypothesis” – i.e. the idea that being exposed to germs in early life somehow helps prime the body against allergy, has been bandied about in the media as a means of explaining the surge in people experiencing allergy in the last few decades. In particular, the blame for allergy has been laid at the door of ultra clean homes. The reason for the rise in allergy incidence is probably far more complicated, however.

“When the hygiene hypothesis was first proposed in 1989, it was suggested that children who had more infections were less likely to develop allergies,” says Professor Sally Bloomfield, honorary Professor at the London School of Hygiene and Tropical Medicine, chairman of the International Scientific Forum on Home Hygiene (IFH) and a former pharmacist. “However, it became clear after a while that it wasn’t harmful organisms, such as those that cause childhood infections, which were having the impact on people’s risk of allergy.” In 2003, Professor Graham Rook came up with what he called the “old friends mechanism”, reasoning that it was loss of contact with the nonharmful organisms – the kind that early humans evolved with – that was behind the rise in allergy.

The thinking, explains Professor Bloomfield, is that if we’re not exposed, particularly in early life, to these “old friends” (microbes that live on our skin, in our guts, on animals and in the natural environment), “the immune system won’t be properly regulated and may therefore overreact, as in hayfever and other allergies.” It also seems likely that exposure to a diverse range of species is important, Professor Bloomfield adds. Indeed, a recent BBC Horizon programme put the lives of two allergenic families under the microscope and found that they had far fewer types of bacteria living on them and in them than people living in traditional tribes in parts of the developing world – where incidence of allergy was, interestingly, rare.

It’s thought that a whole range of factors has reduced our exposure to our “old friend” microbes. “One of the most important changes in the past 200 years has been the introduction of good sanitation, clean water and the clean-up of city streets,” says Professor Bloomfield. “Yes, this has protected us from infectious diseases, but it has also cut us off from “old friends” as these microbes largely inhabit the same environment as harmful ones.

Of course, we don’t want to reverse that progress and invite infections back.” Other, more recent trends, she suggests, have also led to a reduction in our exposure to “old friends”, including having smaller families, an increase in children being born by caesarean section – as babies are exposed to a variety of different microbes as they move through the birth canal, and a reduction in breastfeeding. One Norwegian study found that children delivered by caesarean section had an increased risk of developing asthma.

There is also evidence that antibiotics may be involved. One study, published in the British Journal of Dermatology, suggested that the use of antibiotics in the first year of life may increase a child’s risk of developing eczema by up to 40 per cent. And there’s the fact that so much of our time is now spent indoors.

“Most of us live in concrete cities and are thus not in contact with the rural environment, where there is good microbial diversity,” says Professor Bloomfield. It is not all about microbes, however. Many other factors will influence a person’s risk of developing an allergy, “including diet, pollution, obesity and stress,” says Professor Bloomfield.

“Genetic predisposition is also a risk factor and this may explain why we do not all suffer from allergies.” If it is true that microbial exposure plays an essential role in regulating the immune system to prevent it overreacting to allergens, how can this knowledge be used to reverse the trend in allergy? Unfortunately, the answer to this is, as yet, unclear.

“It is possible that promoting a healthy and balanced lifestyle could reduce the risk of developing allergies, but as yet we have no proof,” says Professor Bloomfield. She is adamant, however, about one thing – and that is that people are not misled by the name “hygiene hypothesis” into thinking they can relax their hygiene standards. “If we abandon hygiene practices such as handwashing before eating and after going to the toilet or cleaning food surfaces after contact with raw foods, this will simply increase the risk of developing infectious diseases,” she says.

“Get children outdoors and let them get dirty, but make sure they wash their hands before eating. Good hygiene in our homes and everyday lives is as important as it ever was, but we need to target our hygiene practices in the places and at the times that it matters, such as food and respiratory hygiene, toilet hygiene, and so on.”

The hygiene hypothesis does not mean we should abandon practices such as handwashing

 

Hayfever

Hayfever is the most common allergy – nearly 18 million people in the UK suffer from it, according to Allergy UK – so it’s hard to believe that 200 years ago, no one had even heard of it. The incidence of hayfever varies from year to year, depending on the weather, but last year brought with it a new worry: ragweed pollen. Its detection in the UK triggered fears that the plant ragweed – responsible for many cases of in search of the missing half a million hayfever in other parts of Europe and in the US – may be on its way here.

Researchers at the University of Leicester, in collaboration with the Midlands Asthma and Allergy Research Association, have been examining pollen and fungal spore levels in the East Midlands since 1970. Last September, they reported detecting ragweed pollen on four consecutive days. “This was very surprising,” says Dr Catherine Pashley, a research fellow who runs the aerobiology and clinical mycology group at the University of Leicester.

“We have records for the East Midlands dating back to 1970 and ragweed pollen has only previously been observed in six of those years, but never higher than a daily average of five grains, and never on four consecutive days. In 2014, the highest daily average we found was 35 grains.” It was a cause for concern, she says, “because this level of pollen could cause allergies in individuals allergic to ragweed. Ragweed is one of the most wellknown triggers for hayfever in North America and is becoming notorious within certain areas of Europe.”

If ragweed was to appear in the UK, it would be worrying news for hayfever sufferers. “The naturalisation of ragweed plants in the UK is a great health concern to the allergic population,” says Dr Pashley. “Less than 20 years since its appearance in Northern Italy, ragweed pollen has become the second most frequent cause of respiratory allergy there, as well as the one causing the most symptoms and has been responsible for new allergies developing in older individuals.” It’s hard to know yet whether the presence of ragweed last autumn was a one-off or indicative of something more worrying.

Says Dr Pashley: “In the 1990s, it was estimated that if climate change forecasts occurred and the annual average temperatures in Europe increased at a rate of 0.2°C a decade, ragweed could spread north and be persistent as far as central England by the year 2050. It is possible that what we observed was the start of this predicted spread into the UK of ragweed, but it is too early to say for definite.” If the spread of ragweed occurs, we’ll need to be prepared for ragweed pollen allergy during the autumn months – a time when hayfever sufferers can usually relax in the knowledge that the hayfever season is done and dusted for another year.

Food allergy

Allergy UK says that there has been a significant increase in the incidence of food allergies, particularly among children. Six to eight per cent of children in the UK are now thought to have a proven food allergy. But there has been a stir of excitement this year among researchers and health professionals seeking ways of trying to curb the rise.

New research from King’s College London suggests that eating peanuts at an early age may protect high-risk infants from developing a peanut allergy. The LEAP (Learning Early About Peanut Allergy) study, published in the New England Journal of Medicine, involved 640 children considered to be at high risk of developing a peanut allergy because of severe eczema and/or an egg allergy. It was carried out to see whether peanut consumption or avoidance was the most effective strategy for preventing peanut allergy.

The researchers concluded that early, sustained consumption of peanuts was associated with a substantial and significant decrease in the development of peanut allergy in high-risk infants by the age of five years. Although this was an exciting result, they warned that parents of infants and young children with eczema and/or an egg allergy should consult with an allergist, paediatrician or GP before feeding the child peanut products – this study was not a “try-it at home” experiment. They also noted that the study excluded infants showing early signs of having already developed a peanut allergy.

Professor Simon Murch of the Royal College of Paediatrics and Child Health commented that the study was “potentially a very significant moment as it demonstrates that turning around our current approach may give better results”. It will be interesting to see what further research reveals. There has been good news for the two million people in the UK living with food allergy, meanwhile, as new EU rules that came into effect in December 2014 mean they should now be able to buy food and eat out with more confidence.

The new Food Information Regulation makes it a requirement by law that food businesses provide information about the allergenic ingredients used in any food they provide or sell. Under the new regulations, restaurants and takeaways are required to tell customers if any of the main 14 food allergen ingredients, which include peanuts, celery, cereals containing gluten, eggs, fish, lupin and milk, are in the food they serve. The new rules will also change the way allergy information appears on labelling for pre-packed foods bought in shops and supermarkets.

It is hoped the rules will reduce the number of reactions caused by people accidentally eating food they are allergic to. The Food Standards Agency says that, on average, 10 people die and about 5,000 are hospitalised each year because of allergic reactions, and that the majority of these deaths and hospitalisations are caused by incorrect information being given about allergenic ingredients in foods when eating out. This year’s Allergy Awareness Week, running from 20-26 April, focuses on the serious side of allergies and the potentially fatal consequences for sufferers.

“Severe allergic reactions, also known as anaphylaxis, are a daily worry for those living with allergies in the UK,” says Maureen Jenkins, clinical director for Allergy UK. “The week will aim to educate the public on how serious allergic reactions can be, how to recognise the signs of anaphylaxis and what to do in an emergency situation.” The symptoms of a severe food allergic reaction include tingling of the lips; swelling of the lips, tongue and throat; difficulty breathing, and faintness. These are very different to the symptoms of food intolerance, which include bloating, nausea, migraine, joint pain and irritable bowel syndrome (IBS).

 

Food intolerance

The number of people who think they have a food intolerance has increased substantially in the last few years and experts worry that too many people are self-diagnosing themselves and leaving out certain foods from their diet without informed help or advice. The “free-from” foods market is growing – in the UK we spend more than £200 million on freefrom products every year. Tanya Thomas, a dietitian and spokesperson for the British Dietetic Association, believes there are a number of reasons behind this, including the rise in diagnosis of coeliac disease; awareness of non-coeliac gluten intolerance; people trying glutenfree or dairy-free diets for autism; mass celebrity hype about the perceived benefits of gluten-free, wheat-free and dairy-free diets; and people experiencing mild gut symptoms and removing gluten, diary or wheat from their diet.

“I think a lot of people are keen to get on the band wagon of ‘free-from’, especially if they have IBS symptoms,” says Tanya. Bloating, for instance, may not be a result of gluten, she says. “It’s important to get other conditions excluded first, as bloating could be the result of something more serious. Going gluten-free is not necessarily healthier, as many gluten-free products are high in fat and sugar.” Bloating can be caused by over-indulgence, bacterial overgrowth or other food stuffs, not necessarily gluten, she adds. Her advice is that anyone who thinks they may have a food intolerance should seek medical advice before embarking on any exclusion diet.

Signposting

• Home, Hygiene and Health – for more information about targeted hygiene
• Coeliac UK
• Allergy UK

 

Six to eight per cent of children in the UK are now thought to have a proven food allergy