Australia has often been called the “allergy capital of the world”.

An estimated one in ten Australian children develop a food allergy in their first 12 months of life. Research has previously suggested food allergies are more common in infants in Australia than infants living in Europe, the United States or Asia.

So why are food allergies so common in Australia? We don’t know exactly – but local researchers are making progress in understanding childhood allergies all the time.

What causes food allergies?

There are many different types of reactions to foods. When we refer to food allergies in this article, we’re talking about something called IgE-mediated food allergy. This type of allergy is caused by an immune response to a particular food.

Reactions can occur within minutes of eating the food and may include swelling of the face, lips or eyes, “hives” or welts on the skin, and vomiting. Signs of a severe allergic reaction (anaphylaxis) include difficulty breathing, swelling of the tongue, swelling in the throat, wheeze or persistent cough, difficulty talking or a hoarse voice, and persistent dizziness or collapse.

Recent results from Australia’s large, long-running food allergy study, HealthNuts, show one in ten one-year-olds have a food allergy, while around six in 100 children have a food allergy at age ten.

In Australia, the most common allergy-causing foods include eggs, peanuts, cow’s milk, shellfish (for example, prawn and lobster), fish, tree nuts (for example, walnuts and cashews), soybeans and wheat.

Allergies to foods like eggs, peanuts and cow’s milk often present for the first time in infancy, while allergies to fish and shellfish may be more common later in life. While most children will outgrow their allergies to eggs and milk, allergy to peanuts is more likely to be lifelong.

Findings from HealthNuts showed around three in ten children grew out of their peanut allergy by age six, compared to nine in ten children with an allergy to egg.

Are food allergies becoming more common?

Food allergies seem to have become more common in many countries around the world over recent decades. The exact timing of this increase is not clear, because in most countries food allergies were not well measured 40 or 50 years ago.

We don’t know exactly why food allergies are so common in Australia, or why we’re seeing a rise around the world, despite extensive research.

But possible reasons for rising allergies around the world include changes in the diets of mothers and infants and increasing sanitisation, leading to fewer infections as well as less exposure to “good” bacteria. In Australia, factors such as increasing vitamin D deficiency among infants and high levels of migration to the country could play a role.

In several Australian studies, children born in Australia to parents who were born in Asia have higher rates of food allergies compared to non-Asian children. On the other hand, children who were born in Asia and later migrated to Australia appear to have a lower risk of nut allergies.

Meanwhile, studies have shown that having pet dogs and siblings as a young child may reduce the risk of food allergies. This might be because having pet dogs and siblings increases contact with a range of bacteria and other organisms.

This evidence suggests that both genetics and environment play a role in the development of food allergies.

We also know that infants with eczema are more likely to develop a food allergy, and trials are underway to see whether this link can be broken.

Can I do anything to prevent food allergies in my kids?

One of the questions we are asked most often by parents is “can we do anything to prevent food allergies?”.

We now know introducing peanuts and eggs from around six months of age makes it less likely that an infant will develop an allergy to these foods. The Australasian Society of Clinical Immunology and Allergy introduced guidelines recommending giving common allergy-causing foods including peanut and egg in the first year of life in 2016.

Our research has shown this advice had excellent uptake and may have slowed the rise in food allergies in Australia. There was no increase in peanut allergies between 2007–11 to 2018–19.

Introducing other common allergy-causing foods in the first year of life may also be helpful, although the evidence for this is not as strong compared with peanuts and eggs.

What next?

Unfortunately, some infants will develop food allergies even when the relevant foods are introduced in the first year of life. Managing food allergies can be a significant burden for children and families.

Several Australian trials are currently underway testing new strategies to prevent food allergies. A large trial, soon to be completed, is testing whether vitamin D supplements in infants reduce the risk of food allergies.

Another trial is testing whether the amount of eggs and peanuts a mother eats during pregnancy and breastfeeding has an influence on whether or not her baby will develop food allergies.

For most people with food allergies, avoidance of their known allergens remains the standard of care. Oral immunotherapy, which involves gradually increasing amounts of food allergen given under medical supervision, is beginning to be offered in some facilities around Australia. However, current oral immunotherapy methods have potential side effects (including allergic reactions), can involve high time commitment and cost, and don’t cure food allergies.

There is hope on the horizon for new food allergy treatments. Multiple clinical trials are underway around Australia aiming to develop safer and more effective treatments for people with food allergies.

Jennifer Koplin, Group Leader, Childhood Allergy & Epidemiology, The University of Queensland and Desalegn Markos Shifti, Postdoctoral Research Fellow, Child Health Research Centre, Faculty of Medicine, The University of Queensland

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

What’s the difference? is a new editorial product that explains the similarities and differences between commonly confused health and medical terms, and why they matter.

The term “man flu” takes a humorous poke at men with minor respiratory infections, such as colds, who supposedly exaggerate their symptoms.

According to the stereotype, a man lies on the sofa with a box of tissues. Meanwhile his female partner, also with a snotty nose, carries on working from home, doing the chores and looking after him.

But is man flu real? Is there a valid biological reason behind men’s symptoms or are men just malingering? And how does man flu differ from flu?

What are the similarities?

Man flu could refer to a number of respiratory infections – a cold, flu, even a mild case of COVID. So it’s difficult to compare man flu with flu.

But for simplicity, let’s say man flu is actually a cold. If that’s the case, man flu and flu have some similar features.

Both are caused by viruses (but different ones). Both are improved with rest, fluids, and if needed painkillers, throat lozenges or decongestants to manage symptoms.

Both can share similar symptoms. Typically, more severe symptoms such as fever, body aches, violent shivering and headaches are more common in flu (but sometimes occur in colds). Meanwhile sore throats, runny noses, congestion and sneezing are more common in colds. A cough is common in both.

What are the differences?

Flu is a more serious and sometimes fatal respiratory infection caused by the influenza virus. Colds are caused by various viruses such as rhinoviruses, adenoviruses, and common cold coronaviruses, and are rarely serious.
Colds tend to start gradually while flu tends to start abruptly.

Flu can be detected with laboratory or at-home tests. Man flu is not an official diagnosis.

Severe flu symptoms may be prevented with a vaccine, while cold symptoms cannot.

Serious flu infections may also be prevented or treated with antiviral drugs such as Tamiflu. There are no antivirals for colds.

OK, but is man flu real?

Again, let’s assume man flu is a cold. Do men really have worse colds than women? The picture is complicated.

One study, with the title “Man flu is not a thing”, did in fact show there were differences in men’s and women’s symptoms.

This study looked at symptoms of acute rhinosinusitis. That’s inflammation of the nasal passages and sinuses, which would explain a runny or stuffy nose, a sinus headache or face pain.

When researchers assessed participants at the start of the study, men and women had similar symptoms. But by days five and eight of the study, women had fewer or less-severe symptoms. In other words, women had recovered faster.

But when participants rated their own symptoms, we saw a somewhat different picture. Women rated their symptoms worse than how the researchers rated them at the start, but said they recovered more quickly.

All this suggests men were not exaggerating their symptoms and did indeed recover more slowly. It also suggests women feel their symptoms more strongly at the start.

Why is this happening?

It’s not straightforward to tease out what’s going on biologically.

There are differences in immune responses between men and women that provide a plausible reason for worse symptoms in men.

For instance, women generally produce antibodies more efficiently, so they respond more effectively to vaccination. Other aspects of women’s immune system also appear to work more strongly.

So why do women tend to have stronger immune responses overall? That’s probably partly because women have two X chromosomes while men have one. X chromosomes carry important immune function genes. This gives women the benefit of immune-related genes from two different chromosomes.

Oestrogen (the female sex hormone) also seems to strengthen the immune response, and as levels vary throughout the lifespan, so does the strength of women’s immune systems.

Men are certainly more likely to die from some infectious diseases, such as COVID. But the picture is less clear with other infections such as the flu, where the incidence and mortality between men and women varies widely between countries and particular flu subtypes and outbreaks.

Infection rates and outcomes in men and women can also depend on the way a virus is transmitted, the person’s age, and social and behavioural factors.

For instance, women seem to be more likely to practice protective behaviours such as washing their hands, wearing masks or avoiding crowded indoor spaces. Women are also more likely to seek medical care when ill.

So men aren’t faking it?

Some evidence suggests men are not over-reporting symptoms, and may take longer to clear an infection. So they may experience man flu more harshly than women with a cold.

So cut the men in your life some slack. If they are sick, gender stereotyping is unhelpful, and may discourage men from seeking medical advice.

Thea van de Mortel, Professor, Nursing, School of Nursing and Midwifery, Griffith University

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