Tough nuts: why peanuts trigger such powerful allergic reactions



The humble peanut. Tasty for most, treacherous for some.
Dr Dwan Price, Author provided

Dwan Price, Deakin University

Food allergens are the scourge of the modern school lunchbox. Many foods contain proteins that can set off an oversized immune reaction and one of the fiercest is the humble peanut.

Around 3% of children in Australia have a peanut allergy, and only 1 in 5 of them can expect to outgrow it. For these unlucky people, even trace amounts of peanut can trigger a fatal allergic reaction.

But what sets the peanut apart from other nuts? Why is it so good at being an allergen?

To answer this, we have to explore the pathway from allergen to allergy, and just what it is about an allergen that triggers a response from the immune system.




Read more:
What are allergies and why are we getting more of them?


How food gets to the immune system

Before coming into contact with the immune system, an allergen in food needs to overcome a series of obstacles. First it needs to pass through the food manufacturing process, and then survive the chemicals and enzymes of the human gut, as well as cross the physical barrier of the intestinal lining.

After achieving all of this, the allergen must still have the identifying features that trigger the immune system to respond.

Many food allergens successfully achieve this, some better than others. This helps us to understand why some food allergies are worse than others.

The most potent allergens – like peanuts – have many characteristics that successfully allow them to overcome these challenges, while other nuts display these traits to a lesser extent.

Strength in numbers

The first characteristic many allergenic foods have, especially peanuts, is strength in numbers. Both tree nuts and peanuts contain multiple different allergens. At last count, cashews contain three allergens, almonds have five, walnuts and hazelnuts have 11 each and peanuts are loaded with no less than 17.

Each allergen has a unique shape, so the immune system recognises each one differently. The more allergens contained in a single food, the higher the potency.
Additionally, many of these allergens also have numerous binding sites for both antibodies and specialised immune cells, further increasing their potency.

Stronger through scorching

The first hurdle for a food allergen is the food manufacturing process. Many nuts are roasted prior to consumption. For most foods, heating changes the structure of proteins in a way that destroys the parts that trigger an immune response. This makes them far less potent as allergens.

This is not the case for many tree nuts: allergens in almonds, cashews and hazelnuts survived roasting with no loss of potency.

And for the major peanut allergens, it’s even worse. Roasting actually makes them more potent.




Read more:
Can I prevent food allergies in my kids?


The gauntlet of the gut

From here, the allergen will have to survive destruction by both stomach acid and digestive enzymes within the human gut. Many nut allergens have the ability to evade digestion to some degree.

Some simply have a robust structure, but peanut allergens actively inhibit some of the digestive enzymes of the gut. This helps them safely reach the small intestine, where the allergens then need to cross the gut lining to have contact with the immune system.

This is where peanut allergens really stand apart from most other allergens. They have the ability to cross the intestinal cells that make up the gut lining. Given their relative sizes, this is like a bus squeezing itself through a cat flap.

Peanut allergens accomplish this remarkable feat by altering the bonds that hold the gut cells together. They can also cross the lining by hijacking the gut’s own ability to move substances. Once across, the allergens will gain access to the immune system, and from there an allergic response is triggered.

Peanut allergens attack the bonds that hold intestinal cells together.
Dr Dwan Price, Author provided

The combination of multiple allergens, numerous immune binding sites, heat stability, digestion stability, enzyme blocking, and the effect on the gut lining makes peanut a truly nasty nut.

Where to from here?

This leaves us with a nagging question: if peanuts are so potent, why doesn’t everyone develop a peanut allergy? We still don’t know.

Recently, a potential vaccine developed by researchers from the University of South Australia has shown promise in reprogramming the immune system of mice and blood taken from people with peanut allergy. Will this translate to a potential treatment for peanut allergy? We will have to wait and see.

For now, the more we learn about the action of allergens, and the more we understand their effects on our body, the more we can develop new ways to stop them. And eventually, we might outsmart these clever nuts for good.The Conversation

Dwan Price, Molecular Biologist and Postdoc @ Deakin AIRwatch pollen monitoring system., Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How to manage grass pollen exposure this hay fever season: an expert guide



Spring has sprung, which means it’s hay fever season.
From shutterstock.com

Janet Davies, Queensland University of Technology; Connie Katelaris, South Western Sydney Local Health District, and Danielle Medek, Australian National University

Nearly one in five Australians are affected by hay fever. If you’re one of the unlucky ones, you’ll know how troublesome the symptoms can be.

Grass pollen is the major outdoor trigger of hay fever and allergic asthma. Pollen grains contain a variety of allergens that can trigger allergic reactions in people who are sensitised to pollen.

The good news is, if pollen is a problem for you, there are things you can do to manage your exposure to it. By adopting some simple tips alongside preventative medications, you may find this hay fever season a little more manageable.




Read more:
How do you know if your child has hay fever and how should you treat it?


What causes hay fever?

People who are genetically prone to develop allergies may become sensitised to pollen.

Sensitisation involves development of specific antibodies (called Immunoglobulin E, or IgE) that can bind to the triggering allergen. Repeated exposure to the triggering allergen leads to the activation of inflammatory cells, causing the release of histamine and other mediators. That’s when the symptoms kick in.

An allergic reaction to pollen can lead to hay fever symptoms affecting the upper airways, including itchy, watery eyes, an itchy, inflamed throat, a runny or blocked nose, and sneezing.

Pollen allergy can also lead to what we call allergic asthma – if the allergen components enter deeper into the lungs, this can cause inflammation and symptoms of asthma, like shortness of breath.

While hay fever has long been regarded a trivial condition, it can be a serious chronic disease associated with other problems such as sinusitis, sleep disturbance because of nasal blockage, and asthma, leading to fatigue and poor performance at work or school.

What can you do to reduce exposure to pollen allergens?

The tragic thunderstorm asthma epidemic of November 2016 in Melbourne shocked many and elucidated the potential harm of grass pollen exposure.

Lessons from this event illustrate staying indoors with the windows closed reduces risk of experiencing severe symptoms.

Many people affected by thunderstorm asthma recall being outside prior to the passage of the thunderstorm across the greater Melbourne region during the late evening of November 21, 2016.




Read more:
What’s the link between hay fever and asthma, and how are they treated?


Of course, this was an uncommon event, and the majority of people who get hay fever will not experience this level of illness.

On high pollen days, or after thunderstorms in spring, people who are allergic to pollen should stay inside with windows closed when possible. They should also drive with the car windows closed and the air on a setting where it’s circulating, rather than coming in from outside.

Other actions people can take to reduce allergen exposure are to hang washing inside or use a tumble dryer on high pollen days, avoid activities such as mowing the lawn, wear sunglasses outdoors, and shower after activities likely to involve pollen exposure.

Close to one in five Australians suffer from hay fever.
From shutterstock.com

A national standardised pollen monitoring network

For people with hay fever, knowing when the pollen count is likely to be high can be helpful in managing exposure. There are an increasing number of mobile apps you can use to monitor the pollen count in your area in real time.

A screenshot from pollen monitoring app ‘Melbourne Pollen Count’.
Screenshot

In 2016, the National Health and Medical Research Council funded the AusPollen Partnership. Since its inception, and with the efforts of many researchers, a national standardised pollen monitoring network is being established to help address unmet needs of patients with hay fever and allergic asthma in our community.

The AusPollen Partnership seeded the growth of a number of projects in which pollen monitoring is a key activity; for instance AirRater in Tasmania and VicTAPS in Victoria. Australian pollen monitoring sites now adopt standard protocols to harmonise pollen monitoring processes so data is comparable between locations.

While expanding the pollen monitoring network, we’ve had the opportunity to evaluate how providing people with local, current daily pollen information helps.

In a pilot study, we found people who didn’t have access to local pollen information indicated a desire to have local pollen information, while people who did have access to pollen information reported it was very useful. Respondents used pollen information to plan their daily activities, to minimise pollen exposure and to optimise medication use.




Read more:
Health Check: what are the options for treating hay fever?


Preventative medication has an important role

While minimising exposure to pollen may help reduce symptoms when pollen levels are high, the cornerstone to symptom management and safety during the pollen season is preventative medication like steroid nasal sprays and antihistamines. These can reduce the underlying allergic inflammation and alleviate symptoms of hay fever.

Before the onset of the pollen season, people who are allergic to pollen and suffer from troublesome symptoms should start using medications daily. Control of underlying allergic inflammation in the upper airways is best achieved with nasal sprays containing a topically active steroid. Non-sedating antihistamine tablets and eye drops provide symptom relief (but don’t alter the underlying inflammation).

Seasonal asthma and/or thunderstorm asthma can occur during the grass pollen season in some people with pollen allergy. Those who experience lower airway symptoms during the grass pollen season such as a cough, tight chest, breathlessness or wheeze, should seek medical attention to consider whether they have undiagnosed asthma.




Read more:
Thunderstorm asthma: who’s at risk and how to manage it


The Conversation


Janet Davies, Professor, Queensland University of Technology; Connie Katelaris, Professor of Immunology and Allergy, UWAS & Head of Unit, South Western Sydney Local Health District, and Danielle Medek, Physician trainee, researcher, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Think you’re allergic to penicillin? There’s a good chance you’re wrong



File 20190411 2914 mksw66.jpg?ixlib=rb 1.1
A rash people assume is a reaction to penicillin may not be related to the drug at all.
From shutterstock.com

Greg Kyle, Queensland University of Technology

Are you allergic to penicillin? Perhaps you have a friend or relative who is? With about one in ten people reporting a penicillin allergy, that’s not altogether surprising.

Penicillin is the most commonly reported drug allergy. But the key word here is “reported”. Only about 20% of this 10% have a true penicillin allergy – so the figure would be one in 50 rather than one in ten.

People may experience symptoms they think are a result of taking penicillin, but are actually unrelated. If these symptoms are not investigated, they continue with the belief that they should steer clear of penicillin.




Read more:
Weekly Dose: penicillin, the mould that saves millions of lives


This can become a problem if a person is sick and needs to be treated with penicillin. Penicillin and related antibiotics are the most common group of drugs used to treat a broad range of infections, from chest or throat, to urinary tract, to skin and soft tissue infections.

The overestimation of penicillin allergies is also not ideal because it means people are being treated with a broader range of antibiotics than necessary, which contributes to the problem of antibiotic resistance.

Yes, penicillin comes from mould

To understand more about why so many people think they’re allergic to penicillin, we need to look at a brief history of the drug.

Penicillin (benzylpenicillin or Penicillin G) was first discovered in 1928 and first used in 1941.

It was grown from a mould, as it is today. The liquid nutrient broth the mould grew in was drained, and the penicillin purified from it.

In the 1930s and 40s, and even through the 1960s and 70s, purification techniques were not as efficient as they are today. So, many early allergic reactions are thought to be due to impurities in the early penicillin products – especially injections.

Penicillin is now more versatile and can kill a wider range of bacteria than in its earlier days.
From shutterstock.com

Penicillin and the range of antibiotic compounds that followed it revolutionised how we treat bacterial infections.

This led to widespread, and sometimes inappropriate, use of these medicines. Antibiotics do not work against viruses, but are sometimes prescribed for bacterial infections that occur while people have viral infections such as glandular fever.

We know using penicillin while a person has glandular fever can cause a rash that looks like penicillin allergy but is not related.

People may report symptoms to their health professionals that seem like a reaction to penicillin. Perhaps these symptoms are not fully investigated because it takes time and can be expensive – they’re just put down to the common penicillin allergy.

Further, some people perceive other side effects of a penicillin antibiotic such as nausea or diarrhoea as an allergy, when these are not, in fact, allergy symptoms.

From this point, the penicillin family will not be used to treat these patients.




Read more:
We know _why_ bacteria become resistant to antibiotics, but _how_ does this actually happen?


The problem of antibiotic resistance

An allergy to penicillin can also limit the use of some other antibiotics which may cross-react with the allergy.

Cross reaction occurs when the chemical structure of another antibiotic is so similar to the structure of penicillin that the immune system gets confused and recognises it as the same thing.

To avoid this, doctors need to look to antibiotics from other medication classes when prescribing patients with a documented penicillin allergy.

But we need to be careful when drawing on a wider range of antibiotics. This is because the more bacteria are exposed to antibiotics, the more likely they are to develop resistance to these antibiotics.

The range of penicillins we have today came from experimenting with the chemistry of the original penicillin molecule and changing its properties.
From shutterstock.com

To address the growing problem of antibiotic resistance, we now try to restrict antibiotics as much as possible to the lowest level one that will kill the specific bacteria.

We don’t kill tiny ants in our gardens with a sledgehammer, so likewise, we use a narrow-spectrum antibiotic wherever possible to keep the broad-spectrum antibiotics for severe and complex infections.

The penicillin family contains both narrow and broad-spectrum antibiotics. Ruling out this family and its “cousins” when we don’t need to can limit the choice of antibiotics and increase the chance of making other antibiotics less useful.

Can I get tested?

Studies show penicillin allergy reduces over time. So even if you did have a true penicillin allergy, it may have gone away over several years.

Under the guidance of your doctor, it is possible to be tested to see if you’re allergic – or still allergic – to penicillin.

A skin “scratch” test involves injecting a small amount of penicillin and monitoring for a reaction. Rescue medications will be on hand in case you do have a severe reaction. Your GP will probably refer you to an allergy specialist to get this done.




Read more:
Common skin rashes and what to do about them


If you have been told you’re allergic, you should first try to find out when the reaction occurred and what happened in as much detail as possible.

Let your GP know all this information and he or she can then decide whether a skin test might be appropriate.

Do not try a test dose at home – the risk of a life-threatening reaction is not worth it.

And if you believe you are allergic to penicillin, the most important thing to do is tell each health professional (doctor, pharmacist, nurse, dentist, etc.) you come into contact with.The Conversation

Greg Kyle, Professor of Pharmacy, Queensland University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.