Category: Academic Analysis

Source: The Conversation – UK – By Jon Gluyas, Professor of Geoenergy, Carbon Capture and Storage, Durham University

Imagine powering long-haul aircraft and heavy ships with fuels derived from just air, water and renewable electricity. This is moving from science fiction to the verge of reality, thanks to the falling price of renewables like wind and solar.

Whereas burning today’s fuels releases carbon into the atmosphere that has been sequestered underground for millions of years, these “e-fuels” would be more environmentally friendly, adding and subtracting carbon from the air in roughly equal quantities.

We’re seeing a glimpse of the future in HIF Global’s Haru Oni project in the south of Chile, backed by Porsche and ExxonMobil. It uses wind power to produce synthetic methanol and gasoline, marking one of the first commercial e-fuel ventures. Similar projects are under development in North Africa, Iceland and the Arabian peninsula, targeting export of e-methanol and e-kerosene.

E-fuels sit within the broader category of synthetic fuels, which are vital for sectors like aviation and shipping that won’t be able to switch to electric power or clean fuels such as hydrogen any time soon.

Synthetic fuels are chemically similar to the energy-dense liquid fuels these modes of transport currently rely on, though its equally possible to produce gases. They still only comprise a tiny share of fuels in these sectors – for instance, around 0.3% of global jet engine fuel was synthetic in 2024.

This is expected to change dramatically in the coming years, potentially rising as high as 50% by 2050. In the meantime, each synthetic fuel comes with trade-offs that affect their costs, scalability and the time to reach the market.

The alternatives

The two other main varieties of synthetic fuel are known as biochemical and thermochemical.

Biochemical fuels are derived either from processing waste fats and oils, or using fermentation or enzymes to transform things like crops and organic waste into alcohols. In both cases, there’s a final step that involves adding hydrogen, in a process called catalytic hydrogenation.

The supply chains are well established for this kind of production, but there’s a lot of competition for the raw materials. They have to be grown on land or water that would otherwise be used for food. Even under optimistic assumptions, these won’t satisfy global demand for sustainable fuels alone.

Thermochemical production uses high temperatures to convert wood residues, waste biomass or even plastics into syngas (a mixture of carbon monoxide and hydrogen). This is then converted into liquid fuels through an industrial process such as Fischer–Tropsch, in which they are heated and run over a catalyst like cobalt.

There’s no need for food feedstocks here, and the industrial processes are proven. However, you must still collect and transport large volumes of feedstock, while the high-temperature plants are expensive. As it stands, the vast majority of today’s synthetic fuels are therefore biochemical, mostly from reprocessing oils.

E-fuels

E-fuels are the newest option. Many leaders in global energy expect them to play a central role in decarbonising aviation and shipping – especially as biomass feedstocks reach their limits. The challenge is that making e-fuels is energy-intensive and currently expensive, particularly where renewable power is scarce or costly. Here’s how it breaks down:

1. Carbon dioxide capture

Capturing and concentrating CO₂ requires about 1-3 megawatt hours (MWh) of energy per tonne, which is fairly significant. Using commercially supplied CO₂ is about one-third the cost of capturing it from the air, so hybrid approaches that use some commercial CO₂ will probably take off first. Commercial CO₂ is usually a byproduct from burning fossil fuels, so this has an environmental downside.

2. Hydrogen production

Even the best methods for extracting hydrogen from water operate at about 70% efficiency. This means that 50–55 kilowatt hours (kWh) of electricity are needed to produce 1kg of hydrogen, which stores only 33 kWh of chemical energy – in other words, considerably more energy goes in than out. This is one reason why making fuels from electricity will probably never be as cheap as using direct electrical power.

3. Compression, storage and transport

Hydrogen must be compressed or liquefied, consuming additional energy (for example, around 10–13 kWh per kg of hydrogen for liquefaction). Hydrogen is also prone to leakage and can embrittle steel pipelines, making long-distance transport difficult.

4. Converting carbon dioxide to fuel

The captured and concentrated C0₂ is converted into fuel by reacting it with hydrogen – or it can first be reduced to carbon monoxide in a catalytic “fuel synthesis” process. In both cases, the resultant product can be an alcohol such as methanol, or a more complex hydrocarbon such as a mixture of paraffins or waxes. Dependent on the desired final product, further processing may be necessary. These steps require high temperatures and pressures, adding energy demand and capital cost.

In sum, each of these four processes compounds energy losses. Until green electricity gets much cheaper, e-fuels will remain a premium product.

In the US and UK, electricity prices are currently around four times greater than natural gas, whereas in Europe it’s about 2.5 times greater. Roughly speaking, e-fuels will remain more expensive than fossil fuels until these prices reach parity. Electricity prices incorporate manufacturing and distribution costs as well as taxes, so we’ll need reductions across the board.

Synthetic fuels comparison

The good news is that the cost of green power should keep falling as the technology gets more efficient. In aviation, recent analysis predicts that most sustainable fuel will be biochemical or thermochemical until 2040, but after that most growth is likely to come from e-fuels. By 2050, these could make up over half of all synthetic fuels.

E-fuels could be made in regions rich in renewables such as North Africa, Patagonia and Iceland — creating new players in the global energy trade. A whole ecosystem involving everything from large-scale renewables to fuel logistics will have to be scaled rapidly to make this industry viable.

In short, the chemistry works but the economics are still catching up. And while e-fuels are an exciting prospect, they’re not a silver bullet. Governments and the energy industry will still need to prioritise the switch to electric power and greater energy efficiency wherever possible.

Jon Gluyas is a named but unremunerated director of sustainable aviation fuels startup Exergic Ltd. There was a significant contribution to this article from Jon’s friend Neil Fowler, a retired industrialist.

– ref. Fuel made from just air, power and water is taking off – but several things are holding it back – https://theconversation.com/fuel-made-from-just-air-power-and-water-is-taking-off-but-several-things-are-holding-it-back-269326

Source: The Conversation – UK – By Haomin Wang, Lecturer in Economics, Cardiff University

Whatever decisions Rachel Reeves makes in her second budget as UK chancellor, it is clear that she needs to find lots of money. Some argue that the best and fairest way of doing this is to raise the taxes of the country’s wealthiest people.

Others feel that such a move will do further harm to the UK’s longstanding problem with productivity, by discouraging investment and entrepreneurship.

Economists describe this as the “equity-efficiency trade-off”, where taxes designed to promote fairness may come at the expense of efficiency and growth, by distorting incentives for work and investment.

But our research suggests that some of the very highest earners can simply ignore that trade-off – because the tax system gives them so much flexibility and choice about what they pay. In the UK for example, the way a business is organised has major implications for how it is taxed.

Sole traders (like a plumber or a freelance writer) and partnerships (an accountancy firm or a garage) are known as “pass-through” businesses. They do not pay corporation tax, with profits instead being passed to the owners and taxed as personal income (at 20%, 40% or 45% depending on the amount).

Limited companies are taxed differently, with profits subject to corporation tax (currently 25% for most firms). And within these parameters, company owners can then choose how they get paid.

If they take a salary, these are taxed as employment income but are deductible from company profits, therefore reducing the corporation tax base. And if they take their pay in the form of dividends, a portion of the company’s profits, these are taxed at lower rates (8.75%, 33.75% or 39.35%).

This flexibility allows entrepreneurs to legally lower their tax bills by adjusting both their business structure and how they take income – whether as salary or dividends. In practice then, wealthy business owners can reclassify their income or reorganise their firms. This gives them much more scope to manage their tax liabilities than ordinary wage earners.

Another difference between the two set-ups is that limited companies tend to be more complex and costly compared to pass-through businesses. But they also enjoy better access to finance, which allows for greater investment and expansion. So when entrepreneurs choose their business structure primarily to reduce taxes, they may sacrifice growth opportunities.

Our research into how entrepreneurs respond to taxation found that when entrepreneurs choose a business structure mainly for tax purposes, it can have an adverse effect on investment.

For example, someone may prefer to avoid the “double taxation” of corporate profits and dividends by remaining a pass-through business. But this limits access to credit and constrains expansion, resulting in a business which operates below its potential.

Fairness and flexibility

We also found that tax avoidance undermines the effectiveness of higher top tax rates. For when governments increase personal income taxes, wealthy business owners can simply restructure their income – by taking less salary and more dividends.

As a result, higher rates do little to raise revenue from the very richest. And regular employees, who cannot reclassify their income, end up carrying a relatively heavier burden.

Our work also suggests that when avoidance opportunities are closed – by aligning the tax treatment of different business forms – governments can raise more revenue and, at the same time, improve productivity and welfare. In other words, well-designed tax policy can promote both fairness and efficiency.

So perhaps discussions about how to raise revenue should move on from its traditional focus on introducing new taxes on wealth or increasing top income tax rates. After all, these kinds of measures may not achieve their goals if those on high incomes can exploit gaps in the tax code to reduce their liabilities.

Instead, with the UK’s economic pressures and rising inequality, politicians should note how existing rules shape incentives and behaviour.

A more promising route may involve revisiting how different forms of income are treated within the current system. Aligning the taxation of salaries and dividends for business owners, and reducing distortions between business structures, could improve both fairness and efficiency.

This would ensure that the tax system rewards productive entrepreneurship – rather than financial engineering.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

– ref. One small change Rachel Reeves could make to close tax loopholes and raise revenue – https://theconversation.com/one-small-change-rachel-reeves-could-make-to-close-tax-loopholes-and-raise-revenue-268079

Source: The Conversation – UK – By Anna Turns, Senior Environment Editor, The Conversation

This roundup of The Conversation’s climate coverage was first published in our award-winning weekly climate action newsletter, Imagine.

As the UN climate summit Cop30 progresses in the Brazilian city of Belém, there’s much debate about the specifics of climate finance targets, whether the transition away from fossil fuels really can be ethical and how renewables are shaping the global economy. Luciana Julião, editor at The Conversation Brasil, has been busy meeting scientists and experts in Belém, the host city in the heart of the Amazon. She shares her behind-the-scenes insights.

What’s it really like on the ground there, aside from negotiations?

This is a huge event with two official venues. The first is the blue zone, where each country has a pavilion with their own event programme featuring academics, activists and environmental changemakers. This is also where the diplomatic negotiations are taking place.

It’s enormous – about the size of 17 football pitches. Discussions have ranged from the mathematical modelling being used to design disaster alerts to the new tech that’s bringing renewables to traditional communities.

About a mile away from that, the other official venue is the green zone which is open to the public. Slightly smaller (the size of 14 football pitches), this is where side events take place, with representatives from environmental charities and other movements plus universities.

Events are happening all over the city and free buses are shuttling delegates and participants between venues. For example, the free zone is a cultural space where there have been artistic gatherings, cultural shows and Brazilian food. The agrizone is a hub for discussions about farming and food production. The science house is inside the beautiful Emilio Goeldi museum of Pará, the first botanic garden in Brazil. And the Cúpula dos Povos (people’s summit) at the Federal University of Pará (home to the world’s biggest Amazon research centre) is where Indigenous communities are hosting events.

Which side events have been most fascinating?

Kerstin Bergentz, a researcher at the Scripps Institution of Oceanography at the University of California, San Diego, is doing her PhD in physical oceanography. At an event in the ocean pavilion, we spoke about how, even though half of the air we breathe comes from plankton, the oceans don’t get a mention in the Paris climate agreement or in most Cop negotiation texts.

“[The ocean is] such an important part of our climate system and our global earth system, but it’s still not getting enough attention on the global climate agenda,” says Bergentz. “We are all 65% water, and billions of people around the world rely on the ocean for their daily food, for sustenance, for their way of life … [The ocean] has absorbed 30% of anthropogenic CO₂ emissions and 90% of the excess heat associated with those emissions.

“Why do we talk about the Amazon rainforest so much but we don’t talk about the ocean? Maybe [it’s partly] a marketing issue … [because the oceans don’t get as much attention as land-based climate issues]. I also think it’s the fact that 41% of the ocean is in what’s called EEZs or exclusive economic zones. So that’s 200 nautical miles from the coastline, right? And that’s governed by individual countries.”

That, she explains, leaves almost 60% of the ocean – the high seas – as no man’s land. “That’s the biggest ecosystem on this planet, but who’s going to be responsible for that?” Of course, in 2026, a new high seas treaty is due to come into force which heralds a new era of ocean governance – if states can balance conservation with a growing scramble for deep-sea resources.

Another session that really resonated with me was about environmental racism.

Mauricio Paixão, professor at the Federal University of Rio Grande do Sul, Brazil, is studying how the consequences of intense floods in 2024 in Brazil’s most southernmost state are far from fair. “We hear a lot in Rio Grande do Sul, that the disaster was democratic, that it affected rich and poor, white and black, but in practice, despite affecting everyone, the recovery was not and is not being equal for all these groups.”

He has been observing how environmental racism has unfolded in two badly affected neighbourhoods: Menino Deus, a wealthy part of the city, and Sarandí, a poor neighbourhood with a large presence of Black people among its residents.

While the disaster affected everyone, the cleanup took longer to reach the neighbourhoods with the largest Black population. Paixão says that it’s “impossible” to separate the economic issues from the social, ethnic and gender issues. “When the water receded two weeks later, it looked like Menino Deus had never experienced a flood before, while Sarandí was still covered in accumulated garbage and mud. This is a very clear indicator of environmental racism.”

He spoke about removing ideas of intention from the environmental racism debate: “I can’t conceive that someone in a management position would say or think, ‘I’m going to take an action thinking about harming the Black population.’ I don’t think that happens. The idea of environmental racism isn’t in the intention, it’s in the consequence. So the fact that people in management positions don’t consider the demands of Sarandí because they are unaware of the demands of Sarandí, shows a disconnect from reality. And if you’re not connected to what’s happening in the city, you’re going to commit an injustice, and injustice in a racialised context implies environmental racism.”

Who is here, who is not?

Officially, 194 parties are here (that is 193 countries plus the EU delegation, out of a total of 198), with 56,118 delegates registered. But there are not many leaders of those nations present. According to official stats, presidents or official representatives are here from only about 70 countries. The absence of the US president is the most noted and commented on. There are so many people here from Indigenous and traditional communities coming closer to climate negotiations than ever before.

What is the Amazon setting actually like?

Belém is in the forest. Take a small boat for a few minutes, and you can navigate through its rivers to an island covered in tropical forest. It’s a wonderful experience.

It’s a very hot city with temperatures around 30-34°C. It’s humid here so it feels so much hotter than that. It also rains a lot. People here in Belem have a saying that they have two different seasons in the year: one in which it rains every day and another in which it rains all day long.

Right now, it’s raining every day. There’s lots of sunshine but usually in the afternoon, rain is torrential and fast. Then within about 15 minutes, the sun is shining again. People often joke when making arrangements by asking, when are we going to meet, before or after the rain?

Is the atmosphere one of hope or frustration?

I’m not covering official negotiations, but the many scientists and participants I have been talking to have told me two things. First, this is the Cop with the highest presence of Indigenous and traditional people. This elevates their perspectives and contributes to a feeling of hope rather than frustration.

Second, this Cop30 needs to be the Cop of implementation, not just discussion. We already have enough paperwork and knowledge, now it’s time to put those decisions and insights into practice and make the changes happen.

So we still don’t know if there will be any significant advances, but I can tell you the feeling is of hope. Let’s see. Time will tell.

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– ref. Behind the scenes in Belém: The Conversation’s report from Brazil’s UN climate summit – https://theconversation.com/behind-the-scenes-in-belem-the-conversations-report-from-brazils-un-climate-summit-269869

Source: The Conversation – UK – By Alex Brown, Associate Professor of Medieval History, Durham University

In medieval England, peasants on some estates were entitled to a range of sick, annual and bereavement leave that could rival those of many workers in the UK today.

British workers are among the least likely in Europe to take sick leave, and lose an estimated 44 days’ worth productivity every year through working while sick. And although most workers are entitled to at least 28 days of annual leave, there is currently no statutory right for employees to take bereavement leave except after the loss of a child under the age of 18.

By comparison – as our new paper shows – peasants on the estate of Ramsey Abbey in Huntingdonshire, England, were entitled to up to a year and a day of leave from working on the lord’s lands if they were sick. Meanwhile widows were granted leave upon the death of their husbands and workers enjoyed plenty of religious feast days and festivals every year.

Not all peasants enjoyed the same level of benefits. Leave entitlements were negotiated between lords and their tenants. Practices, therefore, varied between manors across medieval England. Elsewhere, arrangements were less generous than on the Ramsey estate, and tenants were more generally entitled to a fortnight or month of sick leave.

At the other end of the spectrum, some peasants received no leave if they were ill, such as the tenants of Wisbech in Cambridgeshire, who were instructed that if “he is ill nevertheless, he will do the labour services he owes”.

Customary tenants – known as villeins – were required to perform unpaid work on the lord’s lands in lieu of rent. These obligations were known as labour services or “works”. Depending on the size of a tenant’s landholding, they might be required to work for between a day and three days per week.

The above entitlements did not constitute paid leave in the modern sense but, because tenants were not required to work on the lord’s lands while they were sick, they were effectively excused from many of their rental obligations.

When were peasants sick?

A high number of absences were recorded during the harvest on the Ramsey estate. This may have been for a variety of reasons, including that peasants were overworked and succumbed to exhaustion during the busy harvest season.

With tiredness, workplace accidents that resulted in infirmity were also more likely. Lords may even have been more diligent in tracking absences during the crucial harvest period because replacement labour was so expensive. Finally, tenants themselves may have exaggerated their own illnesses in examples of sick-leave fraud.

Although tenants were entitled to a year and a day of sick leave on the Ramsey estate, most absences did not run for nearly so long in practice. Some sicknesses were very short, such as that of Richard Berenger who was ill for just two days after the harvest in 1343. He missed half a “work” on the lord’s lands.

In contrast, others suffered chronic and debilitating infirmities, such as Richard Colleson of Warboys in Cambridgeshire, who was absent for an entire year in 1347/48, missing 156 “works”.

Such sick leave could cost the lord if they were forced to find a replacement worker. For example, in the absence of the ploughman who was sick for 84 days in 1420/21, the accounts of Battle Abbey in Sussex record a payment of 14 shillings to a man hired in his stead.

Alongside sick leave, tenants were also entitled to a range of other absences. Widows were granted 30 days of leave from performing their labour services upon the death of their husbands. In an unusual example of compassionate leave one Agnes le Reve of Upwood in Huntingdonshire was excused from a single work on two occasions in the winter of 1342/43 because of two deaths in her household.

Peasants also enjoyed a wide range of feast days and religious festivals. In theory, medieval people were not supposed to work on such days, though in practice some were fined in the church courts for working, often on their own lands or earning additional wages on someone else’s lands.

The number of feast days observed varied widely, even between neighbouring manors. On the Ramsey estate, this ranged from just a handful of religious festivals a year to an upper number of around 30.

We should not eulogise the lives of medieval peasants. They were subject to many restrictions which were greatly resented and resulted in punishments such as leyrwite – a fine on villein women for fornication. Yet, given the harsh and repressive realities of life for many medieval peasants, it is all the more surprising that at least some of them were entitled to such a wide range of sick, annual and bereavement leave.

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Research for this article was conducted thanks to funding from a Leverhulme Trust research project grant, ‘Modelling the Black Death and Social Connectivity in Medieval England’.

Dr Grace Owen is a postdoctoral research associate on the Leverhulme-Trust funded project, ‘Modelling the Black Death and Social Connectivity in Medieval England’.

– ref. Medieval peasants enjoyed a surprising range of sick, annual and bereavement leave benefits – https://theconversation.com/medieval-peasants-enjoyed-a-surprising-range-of-sick-annual-and-bereavement-leave-benefits-260163

Source: The Conversation – UK – By Nando Sigona, Professor of International Migration and Forced Displacement and Director of the Institute for Research into International Migration and Superdiversity, University of Birmingham

The UK government’s latest proposals on asylum rest on an incorrect premise. In announcing them, home secretary Shabana Mahmood argued that “illegal migration is tearing our country apart”. But asylum-seeking is not illegal migration.

Asylum is a form of protection granted by a country to a non-citizen who faces persecution in their home country. The right to seek asylum is enshrined in international law, and applies irrespective of how the person travelled to the place where they are seeking protection.

Yet the policies being rolled out collapse two distinct categories into a single threat, to be addressed through deterrence and control. In effect, the category of the asylum seeker is equated to that of “illegal migrant”. Both are discussed as “abusing the system”, “flouting the rules” and “undermining communities”.

The underlying implication is that all asylum seekers are “illegal migrants”. Any system that follows will therefore be built on a distortion. Its consequences will fall not on the minority who try to game the system, but on the overwhelming majority who have legitimate claims for protection.

In 2024, 84,200 applications for asylum were made in the UK, relating to 108,100 individuals. More than 36,500 asylum appeals were lodged against negative decisions, with 48% of them allowed. Recent data show that in the months to March 2025, 47% of initial decisions resulted in the applicant being granted refugee status.

The new asylum measures promise faster decisions on asylum applications, tougher thresholds to be granted status, and expanded detention and removals. In continuity with the previous Conservative government, the rhetoric of “restoring control” makes the direction clear: restrict access to protection, harden the conditions for claiming it, and speed up refusals.

Labour is not hiding its reasoning for this approach. The government explicitly argues that firmer control is needed to prevent “darker forces” from coming into power. This is presented not as a concession to the far right, but as a public rationale for tightening the system. The message is clear: these policies are needed to keep politics steady, not because they improve the asylum system.

The issue is not simply that the proposals are harsh, unethical or likely to be ineffective. They represent a deeper shift: redefining protection as a discretionary favour rather than a legal obligation. Control becomes the primary focus, leaving less space for discussing refugee rights, protection and international obligations.

If asylum is framed as illegality, and settlement is reshaped into a privilege that must be endlessly earned, then our understanding of equal membership – the idea that those lawfully in the UK should enjoy stability and a clear path to full inclusion – is fundamentally altered.

A lifetime review

One of the key proposals is to extend the length of time it takes for a refugee to achieve settlement from five to 20 years. Until recently, settlement – the immigration status that allows a non-UK citizen to live, work and study in the UK without time restrictions – was the expected outcome for anyone granted refugee status. It is also a prerequisite for applying for British citizenship.

The new proposals transform settlement into something that must be continually earned. The path has become longer, more conditional and far more easily disrupted.

This aligns closely with other recent announcements on policies relating to migrants more generally. Higher salary thresholds, more enforcement, extended probationary periods and more complex routes to settlement have all been tabled.

These changes would build a structural disadvantage into the migration system. Non-citizens can live, work and contribute, but their belonging remains conditional. They become long-term residents on a form of probation, their status always open to review. This is more than an administrative change. It creates a hierarchy of membership that shapes lives, futures and families.

For a refugee family, this can mean years of uncertainty: parents unable to plan long-term careers or mortgages; partners and children living with the fear that a change in income, a missed renewal deadline or a shift in political priorities could jeopardise their right to remain.

It can also mean delays or barriers to family reunification, with spouses or children abroad left in limbo while the principal applicant waits to demonstrate continuous compliance. In practice, what should be a path to stability becomes a prolonged period of vulnerability, in which everyday life is overshadowed by the possibility of losing one’s status.

Nando Sigona receives funding from UKRI, Grant No.10061538.

– ref. Asylum is not illegal migration – why the UK government shouldn’t conflate the two – https://theconversation.com/asylum-is-not-illegal-migration-why-the-uk-government-shouldnt-conflate-the-two-270106

Source: The Conversation – UK – By Sheena Cruickshank, Professor in Immunology, University of Manchester

Peanut allergy is one of the most common food allergies, affecting between 1% and 2% of people living in the west. And, for many years, their prevalence has been rising.

But a recent study out of the US shows that the rate of peanut allergy diagnoses in infants has actually declined. It appears this decline may be due to changes in allergy guidelines – highlighting the importance of introducing this common allergen early on.

A food allergy is a type of allergic reaction which occurs when your immune system reacts inappropriately to things it should ignore – such as pollen or certain types of foods. The most common allergic condition is hayfever – a reaction to pollen. Peanut allergy is one of the most common true food allergies – and also the most common cause of fatal food reactions.

The proportion of people with food allergies in England has more than doubled between 2008 and 2018. Similar data in the US showed more than triple the number of people developed a food allergy between 1997 and 2008.

The reasons for these increases are complex and due to many factors – including exposure to environmental pollutants, alterations in the gut microbiome and genetic predisposition. There also appears to be a link between certain inflammatory health conditions (such as atopic dermatitis and an infant’s likelihood of developing a food allergy.

Read more:
What’s behind the large rise in food allergies among children in the UK?

But this latest study has shown that the US appears to have deviated from this overall trend, with peanut allergies actually falling in infants.

The study examined changes in the rates of peanut allergies since 2015. This was the year allergy guidelines in the US changed to encourage infants considered most at risk of food allergy (such as those with atopic dermatitis) to be introduced to peanuts early in life.

Previous research had shown that these guideline changes had resulted in an increase in the number of parents introducing peanuts into their child’s diet by one year of age. The research team wanted to assess whether this had had any affect on peanut allergy rates, too.

They enrolled almost 39,000 children during the pre-guidelines phase (when advice was to avoid peanuts) and around 47,000 in the post-guidelines phase (after 2015). Allergy incidence in both groups was tracked for one to two years.

The research showed that the total rate of peanut allergy decreased from almost 0.8% to 0.5%. This meant fewer at-risk infants developed a peanut allergy following the guideline change.

These findings mirror prior work in the UK showing that early exposure to peanuts before the age of five was linked to a reduced likelihood of developing an allergy.

Food allergy guidelines

In the late-1990s and early 2000s, the burgeoning incidence of food allergies and their life-threatening implications prompted sweeping policy changes in many western countries.

In the UK in 1998 and the US in 2000, guidelines changed to recommend high-risk allergens (such as peanuts) were completely avoided by pregnant women, breastfeeding mothers and infants considered at high risk for allergy.

But these guidelines were made in the absence of any rigorous studies actually showing they’d have a positive effect. Indeed, animal studies had suggested there may be no benefits – showing that eating potential allergens early in life actually invokes an important phenomenon called oral tolerance.

Oral tolerance is where the immune system ignores a potential allergen after it has been introduced to the gut through diet. How oral tolerance develops isn’t fully understood, but involves several mechanisms that help immune cells to be effectively “switched off” so they don’t mistake certain foods for a threat.

But despite the change in advice to avoid peanuts, rates of peanut allergies did not fall.

A major UK review conducted in 2008 consequently showed there was no clear evidence that eating or not eating peanuts (or foods containing peanuts) during pregnancy, while breastfeeding or in early childhood had any effect on the chances of a child developing a peanut allergy. As such, the advice in the UK to avoid peanuts (and eggs) during pregnancy and early childhood was reversed in 2009.

A randomised trial conducted since this policy change came into place showed that among infants considered at high risk of allergy, consistent consumption of peanuts from 11 months of age resulted in an over 80% lower rate of peanut allergy by the age of five compared with children who had avoided peanuts.

Other studies confirmed these findings, which subsequently led to guidelines changing in the US in 2015.

Many questions remain

It’s now increasingly clear that the early introduction of potentially allergic foods may actually benefit us and reduce our risk of developing a life-changing allergy. Nonetheless, there’s much we still don’t understand.

For example, while the mechanisms underpinning oral tolerance are being elucidated, we still don’t know what the best window of age is for safely invoking it.

We also don’t understand why infants with atopic dermatitis are most at risk of developing a food allergy. The hypothesis is that early exposure to food proteins through a disrupted skin barrier is what leads to allergy, as the immune system becomes sensitised to the food.

It’s also important to note that overall, the incidence of food allergies is still increasing. While this recent US study offers hope for preventing some types of food allergies, questions still remain. For example, some people can develop food allergies during adolescence and adulthood. More must be done to understand why this happens.

There are also still barriers impeding access to diagnosis for severe food allergies. This means many at-risk patients have not been diagnosed, so they also have been prescribed potentially life-saving treatments. These trends are magnified for people living in more deprived areas of the country.

Much more needs to be done to answer these questions and tackle food allergies more broadly.

Sheena Cruickshank receives funding from EPSRC and MRC to investigate how environmental factors impact respiratory and gut conditions

– ref. Are peanut allergies actually declining? – https://theconversation.com/are-peanut-allergies-actually-declining-269739