- Those affected by allergies has trebled in the past 20 years to 21 million
- Allergies are partly due to genetic predisposition but also environment
- Part of the problem is thought to be down to improvements in hygiene
- Here, experts explain other surprising factors that affect children's allergies
There seems little doubt that allergies are increasingly common. And now scientists are uncovering intriguing evidence to suggest why.
A recent Swedish study suggested that dishwashers could be responsible for eczema in children. Researchers found youngsters who eat off dishes that have been scrubbed by hand are significantly less likely to develop allergies.
Apparently, dishwashers are too good at getting rid of all the microbes, some of which keep our immune systems healthy.
An allergy is the sign the immune system has overreacted to a normally harmless substance, such as pollen, food and house dust mite. This can result in asthma, when breathing tubes become narrowed and inflamed, and eczema, which affects the skin. It may also trigger sneezing and streaming eyes (hay fever) or skin symptoms (such as hives).
The number of people affected by allergies has trebled in the past 20 years to around 21 million, according to Maureen Jenkins, clinical director of Allergy UK.
While allergies occur partly because of genetic predisposition, our environment is important, too. ‘The rise became a problem 50 years ago when lifestyles and diets changed dramatically,’ says Dr Adrian Morris, an allergy consultant based in Surrey.
Part of the problem is thought to be down to improvements in hygiene. The bacteria that live on our skin, inside our mouths and ears and fill our intestines are vital to our healthy immune systems. The theory is that modern Western lifestyles disrupt the delicate balance of these micro-organisms, and allergies are the consequence.
Here, experts explain the other surprising factors that raise a child’s risk of developing an allergy — which might explain why you have an allergy.
SIBLINGS WILL PROTECT YOU
Having older siblings has been shown to protect against the development of allergic rhinitis and allergy in the first year of life.
In 1989, a study by David Strachan, professor of epidemiology at St George’s Hospital, London, looked at more than 17,000 children born in 1958 and found that the more older siblings they had, the less likely they were to have allergic rhinitis (hay fever).
It’s thought lots of children living together create a healthy immune-boosting microbial ‘soup’, because they all pick up bugs and share bacteria in the home environment, boosting a younger sibling’s protection.
RURAL LIFE CAN BE HEALTHIER
Children born in the countryside are less likely to develop allergies than children raised in the urban sprawl. This is probably because country children are exposed to a wide variety of microbes from animals and their general muck — this seems to protect them from all allergies, not just animal ones.
‘Studies show that children on arable farms without animals are better protected than children in urban areas but less well protected than children who have cows and chickens,’ says Maureen Jenkins, clinical director of Allergy UK. ‘Pets also seem to offer some protection, but you do need more than one.’
Children born in the countryside are less likely to develop allergies because they are exposed to a wide variety of microbes from animals and their general muck (file image)
Strangely, high levels of air pollution are not linked to asthma. In 1991, after the fall of the Berlin Wall, scientists looked at asthma rates Leipzig — a polluted industrial town in East Germany, and Munich, where air pollution levels were lower. ‘The kids in Leipzig were more likely to have respiratory infections but the kids in Munich were much more likely to have asthma,’ says Dr Adrian Morris.
Fumes from diesel engines can worsen allergies. Diesel particles stick to pollen, causing pollen to become a super allergen, far more irritating to the airways than pollen alone. This means asthmatics may feel worse in cities, where there are more diesel vehicles.
ALLERGY DANGERS OF CAESAREAN BIRTH
Babies born by caesarean are five times more likely to develop allergies by the age of two than those born naturally, according to research presented at the American Academy of Allergy, Asthma, and Immunology meeting in 2013.
Today a quarter of babies in the UK are born by caesarean. That is a significant statistic in light of a Norwegian study that found caesarean babies were 52 per cent more likely to suffer from asthma than those delivered naturally.
Babies are exposed to bacteria in the birth canal which seem to help create an ideal culture of gut flora — the healthy bacteria in our digestive systems — explains Dr Carsten Flohr, paediatric allergy specialist at Guy’s and St Thomas’ NHS Foundation Trust.
‘If babies are born without this contact they don’t pick up healthy microbes which seem to help protect them from allergies,’ he says.
EXOTIC FRUITS THAT RAISE FOOD REACTIONS
UK children now eat a wider range of exotic foods than found in our traditional diet. And some experts believe this can explain the threefold food allergy increase in children over the past decade.
‘One theory is children are exposed to foods such as kiwis and mangos which we have not evolved to cope with very well,’ says Dr Morris. ‘We are seeing an increasing number of allergies where these foods are the trigger.’
WINTER BABIES HAVE MORE ALLERGIES
Children under five are 50 per cent more likely to have food allergies if born in autumn or winter, according to a 2010 U.S. study.
The scientists speculated this could be to do with lower levels of vitamin D in these months, which is synthesised in the skin in the presence of sunlight. Low levels of vitamin D have been linked to higher levels of ‘auto-reactive’ T-cells, which have the ability to turn on the body’s immune system. But Dr Morris is sceptical about the link between birth month and allergy.
‘I don’t think this will ever be proven. There are too many other factors which change depending on the seasons.’
COUCH POTATOES MAY BECOME ASTHMATIC
Sedentary lifestyles in front of the telly are linked to obesity, which is a risk factor for asthma.
In one study, published in the American Journal of Epidemiology in August 2013, obese children were 1.16 to 1.37 times more likely to develop asthma than children of normal weight.
This may be because extra body fat causes inflammation, which is involved in the immune response in asthma, said the lead researcher, Mary Helen Black. The extra pounds also might affect the severity of asthma by placing additional weight on a child’s chest.
Sedentary lifestyles in front of the television have been linked to obesity which, in turn, is a risk factor for asthma (file image)
U.S. asthma rates rose swiftly after the arrival of children’s TV shows such as The Mickey Mouse Club, says Thomas Platts-Mills, director of the Division Of Allergy And Clinical Immunology at University of Virginia School Of Medicine.
‘Prior to 1955, children came home from school and went out to play. Now, the population sits around the house in ways children never sat still before,’ he adds.
This is important because research by his group has shown that people tend to sigh fewer times when watching TV, compared with when reading, although they could not explain why.
Without these periodic expansions of the lung, the bronchial smooth muscle suffers, leading to non-specific bronchial reactivity, says Mr Platts-Mills. And as our lives become sedentary we miss out on the bacteria in gardens, adds Maureen Jenkins. ‘Indoors, we are exposed to allergens like mould spores and dust mite droppings, which are common triggers of allergy.’
PREGNANT WOMEN CAN EAT NUTS
Women who are expecting a baby often avoid eating foods such as nuts and eggs, even if they are craving them, for fear of making their child allergic. This is a mistake, according to Dr Morris.
‘Pregnant women should not follow exclusion diets for the sake of reducing the allergy risk of their baby. The opposite seems to be the case,’ he explains.
Taking omega-3 supplements or eating oily fish while pregnant can also reduce future allergy risk (file image)
Indeed, children are less likely to have a nut allergy if their mothers ate nuts while pregnant, a study published in JAMA Pediatrics in 2013 found. The U.S. researchers said their findings supported the theory that exposure to allergens early in life increases tolerance, lowering the risk of allergies.
A new study at King’s College London backs this up, showing that exposing children to peanut products in early life reduced their chances of developing an allergy.
Women who are pregnant often avoid certain types of foods such as nuts and eggs but researchers have found that exposure to allergens early on can increase tolerance and lower allergy risk
Pregnant women who take omega-3 supplements, or eat oily fish, may also be helping to reduce their child’s future allergy risk.
A study published in the British Medical Journal in 2012 said supplementation with omega-3 fatty acids during pregnancy could reduce the risk of babies developing eczema by over a third and halve the risk of an egg allergy. It’s thought omega-3 fats are important for a healthy immune response.
ANTIBIOTICS FOR BABIES MAY TRIGGER ECZEMA
Studies show women who take broad spectrum antibiotics (ie, an antibiotic used to treat a lot of different infections) in the last trimester of pregnancy are more likely to give birth to babies who have allergies.
Giving babies antibiotics early in life is also linked to a greater risk of eczema. Researchers at King’s College London and two other UK centres reviewed data from 20 studies and found that use of antibiotics in early life may increase the risk of eczema by 40 per cent.
This is thought to be because antibiotics kill off ‘good’ bacteria as well as bad, altering the delicate balance of microflora.
EATING PICKLES CAN REDUCE THE RISKS
Pickles and sauerkraut may offer protection. Scientists from the University of Gothenburg looked at 1,000 girls between seven and eight and found their risk of developing an allergy was reduced if they regularly ate fermented foods — such as sauerkraut — and food not industrially processed.
This may be because pickling involves fermentation, which produces healthy bacteria, while processed food is usually stripped of most of its natural microbes.
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