Toddlers who eat fish at least once a month are less likely to develop hay fever in later childhood.
Hay fever – the itchy, sneezy reaction to pollen, dust and fur – is becoming increasingly common in industrialised countries. Some have blamed the fact that children are being exposed to a narrower range of microbes for disrupting our immune systems, but diet may also play a role.
To explore this,  at the University of Gothenburg in Sweden and her team asked over 4000 parents about their children’s diet and lifestyle at one year of age, and then again when they were nearly teenagers.
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Consistent with previous studies, they found that those who grew up on farms with animals were half as likely to develop hay fever – perhaps because they encounter a greater range of microorganisms in infancy.
But they also found that children who ate fish at least once a month when they were one-year-olds were 30 per cent less likely to develop hay fever by the age of 12.
This connection has been hinted at before: for example, a 2003 study found that 4-year-olds were  to suffer from hay fever if they had eaten fish in their first year of life. Other studies have found links between early fish consumption and lower rates of similar allergic diseases like asthma and eczema.
Omega-3s
“Communities that eat lots of fish generally have lower rates of allergic disease and other inflammatory conditions,” says  at Murdoch Children’s Research Institute in Melbourne, Australia. Studies have also found that children whose mothers took  were less likely to develop asthma, eczema and food sensitivities.
If fish protects against allergies, this is probably due to its high omega-3 fatty acid content, says Tang. It’s thought that these have anti-inflammatory properties, but that modern diets increasingly contain omega-6 fatty acids instead. These come from vegetable oils, and may provoke inflammation.
The changing balance between these fatty acids may help explain why allergies have been on the rise in recent decades. “We used to think that margarine was good for you because it’s not animal fat, but it turns out it’s laden with inflammatory omega-6,” says Tang.
However, there may be other reasons why fish is linked to fewer allergies. For example, other nutrients in fish like vitamin D or particular proteins may also have a protective effect. Alternatively, eating fish may simply be a sign of having a healthier lifestyle overall, says Goksör.
Pediatric Allergy and Immunology
Read more: How clean is too clean? The truth about hygiene and your health
