Food allergies are a very modern - and escalating - epidemic. The number of Britons allergic to everyday foods such as cow's milk, eggs, nuts and shellfish has more than doubled in ten years, the latest research shows.

And it's particularly an issue for young children.

While just 0.5 per cent of over-45s are affected, around eight times as many preschoolers – four per cent – now have a serious allergy.

These can cause significant stress to parents, and can even be life-threatening.

Symptoms range from itchy skin, rashes and hives to vomiting, facial swelling, wheezing and chronic conditions such as asthma or eczema.

And for some, the reactions can lead to anaphylaxis – a serious over-reaction of the immune system in response to an allergen which causes the throat and mouth to swell up, restricting the ability to breathe

This causes around ten deaths a year in the UK.

In July 2016, 15-year-old Natasha Ednan-Laperouse, who had several serious food allergies, died after eating a Pret a Manger baguette containing sesame seeds that weren't listed as an ingredient on the label.

Schoolgirl Hannah Jacobs, 13, also died last year after taking a sip from a hot chocolate from Costa Coffee which had been mistakenly made with cow's milk rather than the soya milk her mother had ordered.

Experts say the reason for the rise in such allergies remains unclear, and is likely to be complicated.

Intriguingly, however, there is increasing evidence that while food allergies cannot be entirely prevented, there are some things parents can do – starting in early pregnancy – to reduce the risk of them developing or turning into more serious issues.

Public health nutritionist Dr Emma Derbyshire says: 'Sometimes there's nothing you can do about it and genetics can play a big role. If there are food allergies in the family, or other allergic conditions such as asthma, eczema and hayfever, this can increase the risk in future generations.

'It's also thought that antibiotic use in babies might have a role to play – although you can't avoid using these essential medications if babies need them to fight off an infection, they can affect their developing immune systems by altering the delicate balance of bacteria in the gut, which might make them more sensitive to certain foods.

'There are environmental triggers, too, like air pollution, and the fact that we live cleaner lives where young children aren't exposed to as many bugs and bacteria as they were in the past.

'But there is also growing evidence that there are some things that you can do – starting in pregnancy, but also into the newborn stage. These won't eliminate the risk completely, but could reduce it and might make allergies less severe than they might otherwise have been.

'It's all about what you eat and when.'

Here, then, are Dr Derbyshire's top five tips for eating to beat allergies…

SUNNY SIDE UP: EAT MORE EGGS

They are highly nutritious and contain several key minerals which are important for pregnancy and for the developing child.

But eating eggs during pregnancy and while breastfeeding might also make it less likely that your child will develop an egg allergy, evidence has shown.

One study found that eating four or more eggs a week during pregnancy was linked to higher levels of ovalbumin, a protein found in egg white, in breast milk.

And children born to those women had biological markers in their blood which suggested their immune systems were better developed to tolerate egg – even before they had consumed any egg themselves.

Dr Derbyshire said: 'You're basically sensitising and priming the baby's immune system by eating eggs while you're pregnant and if you're breastfeeding.'

Generations of women were put off eating eggs during pregnancy because Government advice was that eating raw or undercooked eggs could put them at risk of salmonella, which carries a risk to the unborn child.

That Government advice changed in 2017 – as long as women are eating eggs which have a British Red Lion stamp, they come from chickens vaccinated against salmonella and the NHS says they pose no risk to pregnant women or their babies, even if eaten runny or raw.

Dr Emma Derbyshire adds: 'Nutrients such as high-quality protein, vitamin D, choline and folate are particularly critical for babies' development during the first 1001 days [from conception to age two] and eggs are one of the few natural foods that contain all of them.

'But many women mistakenly cut eggs out of their diet during this period, despite previous concerns about food safety and allergy having been overturned. In fact, avoiding eggs could increase the chance of the baby developing an allergy.'

GET ENOUGH OF THE SUNSHINE VITAMIN

About 20 per cent of the UK population doesn't get enough vitamin D – a crucial nutrient that boosts the immune system, helps maintain strong bones and dampens down inflammation.

And research suggests it might be even more important to maintain healthy levels during pregnancy to stave off food allergies.

Although Dr Derbyshire cautions that the science is still emerging, and some of it is conflicting, some studies show infants with low levels of vitamin D are more likely to have egg or peanut allergies.

This can be addressed during pregnancy because, for the first 12 months, infants' stores of vitamin D are based on their mothers' own levels before they were born.

'The evidence is still emerging on this, but it looks like low vitamin D is linked to an increased risk of all sorts of allergic diseases – not just food allergies,' says Dr Derbyshire.

'Studies show links between low vitamin D in mothers and conditions like eczema, asthma and allergic rhinitis.'

The NHS recommends pregnant women take a vitamin D supplement. However, Dr Derbyshire also advises boosting levels by eating vitamin D-rich foods including fish, dairy, egg yolks and mushrooms.

'Make sure you also get out in the sunshine as sunlight naturally triggers your body to produce vitamin D,' she adds.

HOW OILY FISH CAN BOOST A CHILD'S IMMUNE SYSTEM

Studies have shown that taking an omega-3 supplement during pregnancy and while breastfeeding can reduce the risk of a child developing egg allergies and eczema.

The essential nutrient is a type of healthy fat which can protect the heart and brain and is crucial to unborn babies' development.

But experts believe it may also help dampen down a child's immune system and make it less reactive to potential allergens.

In one big analysis of seven trials, pregnant women who took a supplement reduced their child's risk of egg allergy by 42 per cent and peanut allergy by 38 per cent.

'This is another nutrient where shortfalls during pregnancy are linked to allergies,' says Dr Derbyshire.

'You can take a supplement, but the evidence seems to suggest the body is more efficient at taking it from food. So make sure you consume oily fish like sardines, salmon, tuna and mackerel, but also seeds such as flaxseeds and chia and nuts like walnuts. Eggs are also a good natural source, and some other supermarket foods are fortified with omega-3, including bread, spreads and dairy products.'

DON'T CUT OUT ALLERGENS FROM YOUR DIET

Previous Government advice was for pregnant women to avoid eating peanuts and undercooked eggs because it was believed that common allergens could be dangerous to a developing baby.

But experts now believe this well-intentioned advice – now overturned – may have inadvertently led to an increase in allergies in children.

It was dropped in 2009, but the message has been hard to shake off.

'Some women still avoid these things in pregnancy, although they don't have to,' says Dr Derbyshire. 'By fearing you'll expose your unborn child to allergens, you could in fact be giving them an allergy by not exposing them.'

Overall, research shows that the healthier and more varied the mother's diet is in pregnancy, the less likely a child is to develop a food allergy.

A recent study found a diet rich in fruit, vegetables, nuts, and different sources of protein has the greatest protective effect compared to one based on carbohydrate-rich foods such as breads, pies and pasta.

The same principle applies to breastfeeding – which means babies are exposed to tiny amounts of the allergens in breast milk – and when weaning.

'I can understand why parents might be nervous about giving their babies things like peanuts and eggs when there are so many allergies around,' Dr Derbyshire adds. 'But there is a window where we think that, by introducing these foods, you might be able to reduce the risk of allergies.'

That window is generally considered to be between six months and 12 months. Research suggests exposing children after 12 months to an allergen for the first time, such as egg, makes an allergic reaction more likely.

'Introduce each allergen on its own – so you know what's causing the reaction if there is one – and keep a diary to see what happens. Some reactions might take several days to show up. And keep offering the foods rather than thinking, 'Right, I've done cow's milk now, time to move on'. Repeated exposure is key to sensitising children to them.'

If you notice a severe reaction, including breathing difficulties, seek help straight away. But with any reaction, speak to your GP and take their advice before trying that food again.

CONSIDER BREASTFEEDING FOR AT LEAST FOUR MONTHS

Not every woman can (or wants to) breastfeed. But the evidence suggests it can prevent allergies.

'It's thought because babies are being exposed to tiny amounts of allergens they're consuming which leach into breastmilk,' says Dr Derbyshire. 'That might help prime babies' immune systems better so when they do start eating those foods themselves it's less foreign.'

One study has also found that a molecule present in breastmilk might also protect against all sorts of allergic disease. 

The molecule, called miRNA, increases in concentration the longer a baby is breastfed up to a plateau at four months – which may explain why sustained breastfeeding has the most protective effect, the researchers in the US found.