A postcode map of allergies has been produced for the first time, bringing scientists one step closer to uncovering the environmental causes of the severe reactions that affect one in three of the UK population.

By examining almost 6,000 referrals from 672 GPs in Devon and Cornwall over 11 years, as well as consultants’ letters, population data and morbidity statistics, researchers have been able to trace how allergy hotspots develop over time.

“Allergies are on the increase in the UK, but until now, there has been little research into how they differ according to geographical area,” said Ray Jones, from the faculty of health at the University of Plymouth. “Our research also enables us to cross-reference allergies according to a wide range of demographics as well as looking as the co-occurrence of different sorts of allergies in each individual.”

The audit revealed that people are more likely to suffer particular allergies depending on where they live. Airborne allergies, particularly pollen, were clustered in north Dartmoor and Exmoor. Food allergies, particularly nut allergies, were most commonly found in the South Hams. Seafood allergies tended to be found in the far south-west of Cornwall and in the Padstow area.

“We established that there definitely are environmental clusters of single and co-occurring allergies,” said Jones, who co-authored the paper, published today on BioMed Central, an online publisher of 212 peer-reviewed open access journals.

“We have no idea why there are more food allergies in South Hams but there could be more fish allergies in the areas named because there is more physical contact with fish in those areas. There is some research suggesting physical contact can lead to a food allergy.”

More than 20 million people in the UK suffer from, or claim to suffer from, allergies: 44% of adults, according to a recent Mintel survey. Of these, 48% say they have more than one allergy. According to the research, however, only 49% of allergy sufferers have been medically diagnosed.

The UK is poorly equipped for diagnosis and treatment. In 2007, the House of Lords science and technology committee claimed Britain was “the laughing stock of Europe”.

GPs get little or no training about allergies and, the committee found, many patients go untreated.

Misdiagnosis or nondiagnosis are also thought to be responsible for the increase in admissions to English hospitals for anaphylaxis – severe allergic reactions – from 2,821 in 2004–05, to 3,595 in 2008-09.

The National Institute for Health and Clinical Excellence recently issued draft guidelines for GPs urging wider testing. But sufferers are increasingly turning to private clinics, over-the-counter tests and alternative medicines. The allergy remedies market was valued at £110m in 2009, and is forecast to increase by 6% over the next three years.

The study found that almost two-thirds of allergy diagnoses were airborne, with many suffering a combination of pollen, dust-mite and animal-hair allergies.

The survey also found that sensitivities to certain food allergies were likely to go together: patients allergic to dairy products were also likely to have a reaction to eggs, for example. Just 15% of those surveyed had both a food and non-food allergy.

Jones also discovered marked differences in GP referrals to specialist allergy clinics. “The variations between practices were considerable,” he said. “Of 44 practices with Exeter postcodes, one practice referred 25, with the next most frequent referring only seven.”

Potentially fatal childhood peanut allergies mainly affect better-off boys, research has shown. A study found that boys have higher rates of the condition than girls, and children from well-off homes are more likely to be affected than those from poorer backgrounds. More research is needed to explain the trends, say scientists.

The findings, published in the Journal of Allergy and Clinical Immunology, emerged from the health records of more than 400 GP practices in England. The highest rates of allergy were found in children aged five to nine. The research suggests more than 25,000 people in England have been diagnosed with a peanut allergy at some point, a lower figure than previous estimates. It is not clear if this is due to under-recording of cases by GPs.