If you didn’t have food allergies as a child, is it possible to develop them as an adult? The short answer is yes. But the reasons why are much more complicated.

Preschoolers are about four times more likely to have a food allergy than adults and are more likely to grow out of it as they get older.

It’s hard to get accurate figures on adult food allergy prevalence. The Australian National Allergy Council reports one in 50 adults have food allergies. But a US survey suggested as many as one in ten adults were allergic to at least one food, with some developing allergies in adulthood.

What is a food allergy

Food allergies are immune reactions involving immunoglobulin E (IgE) – an antibody that’s central to triggering allergic responses. These are known as “IgE-mediated food allergies”.

Food allergy symptoms that are not mediated by IgE are usually delayed reactions and called food intolerances or hypersensitivity.

Food allergy symptoms can include hives, swelling, difficulty swallowing, vomiting, throat or chest tightening, trouble breathing, chest pain, rapid heart rate, dizziness, low blood pressure or anaphylaxis.

IgE-mediated food allergies can be life threatening, so all adults need an action management plan developed in consultation with their medical team.

Here are four IgE-mediated food allergies that can occur in adults – from relatively common ones to rare allergies you’ve probably never heard of.

1. Single food allergies

The most common IgE-mediated food allergies in adults in a US survey were to:

• shellfish (2.9%)
• cow’s milk (1.9%)
• peanut (1.8%)
• tree nuts (1.2%)
• fin fish (0.9%) like barramundi, snapper, salmon, cod and perch.

In these adults, about 45% reported reacting to multiple foods.

This compares to most common childhood food allergies: cow’s milk, egg, peanut and soy.

Overall, adult food allergy prevalence appears to be increasing. Compared to older surveys published in 2003 and 2004, peanut allergy prevalence has increased about three-fold (from 0.6%), while tree nuts and fin fish roughly doubled (from 0.5% each), with shellfish similar (2.5%).

While new adult-onset food allergies are increasing, childhood-onset food allergies are also more likely to be retained into adulthood. Possible reasons for both include low vitamin D status, lack of immune system challenges due to being overly “clean”, heightened sensitisation due to allergen avoidance, and more frequent antibiotic use.

2. Tick-meat allergy

Tick-meat allergy, also called α-Gal syndrome or mammalian meat allergy, is an allergic reaction to galactose-alpha-1,3-galactose, or α-Gal for short.

Australian immunologists first reported links between α-Gal syndrome and tick bites in 2009, with cases also reported in the United States, Japan, Europe and South Africa. The US Centers for Disease Control estimates about 450,000 Americans could be affected.

The α-Gal contains a carbohydrate molecule that is bound to a protein molecule in mammals.

The IgE-mediated allergy is triggered after repeated bites from ticks or chigger mites that have bitten those mammals. When tick saliva crosses into your body through the bite, antibodies to α-Gal are produced.

When you subsequently eat foods that contain α-Gal, the allergy is triggered. These triggering foods include meat (lamb, beef, pork, rabbit, kangaroo), dairy products (yoghurt, cheese, ice-cream, cream), animal-origin gelatin added to gummy foods (jelly, lollies, marshmallow), prescription medications and over-the counter supplements containing gelatin (some antibiotics, vitamins and other supplements).

Tick-meat allergy reactions can be hard to recognise because they’re usually delayed, and they can be severe and include anaphylaxis. Allergy organisations produce management guidelines, so always discuss management with your doctor.

3. Fruit-pollen allergy

Fruit-pollen allergy, called pollen food allergy syndrome, is an IgE-mediated allergic reaction.

In susceptible adults, pollen in the air provokes the production of IgE antibodies to antigens in the pollen, but these antigens are similar to ones found in some fruits, vegetables and herbs. The problem is that eating those plants triggers an allergic reaction.

The most allergenic tree pollens are from birch, cypress, Japanese cedar, latex, grass, and ragweed. Their pollen can cross-react with fruit and vegetables, including kiwi, banana, mango, avocado, grapes, celery, carrot and potato, and some herbs such as caraway, coriander, fennel, pepper and paprika.

Fruit-pollen allergy is not common. Prevalence estimates are between 0.03% and 8% depending on the country, but it can be life-threatening. Reactions range from itching or tingling of lips, mouth, tongue and throat, called oral allergy syndrome, to mild hives, to anaphylaxis.

4. Food-dependent, exercise-induced food allergy

During heavy exercise, the stomach produces less acid than usual and gut permeability increases, meaning that small molecules in your gut are more likely to escape across the membrane into your blood. These include food molecules that trigger an IgE reaction.

If the person already has IgE antibodies to the foods eaten before exercise, then the risk of triggering food allergy reactions is increased. This allergy is called food-dependent exercise-induced allergy, with symptoms ranging from hives and swelling, to difficulty breathing and anaphylaxis.

Common trigger foods include wheat, seafood, meat, poultry, egg, milk, nuts, grapes, celery and other foods, which could have been eaten many hours before exercising.

To complicate things even further, allergic reactions can occur at lower levels of trigger-food exposure, and be more severe if the person is simultaneously taking non-steroidal inflammatory medications like aspirin, drinking alcohol or is sleep-deprived.

Food-dependent exercise-induced allergy is extremely rare. Surveys have estimated prevalence as between one to 17 cases per 1,000 people worldwide with the highest prevalence between the teenage years to age 35. Those affected often have other allergic conditions such as hay fever, asthma, allergic conjunctivitis and dermatitis.

Allergies are a growing burden

The burden on physical health, psychological health and health costs due to food allergy is increasing. In the US, this financial burden was estimated as $24 billion per year.

Adult food allergy needs to be taken seriously and those with severe symptoms should wear a medical information bracelet or chain and carry an adrenaline auto-injector pen. Concerningly, surveys suggest only about one in four adults with food allergy have an adrenaline pen.

If you have an IgE-mediated food allergy, discuss your management plan with your doctor. You can also find more information at Allergy and Anaphylaxis Australia.

Clare Collins, Laureate Professor in Nutrition and Dietetics, University of Newcastle

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.