Child food allergy tests could be ‘unreliable’

False readings could mean some youngsters are still suffering. Picture: Getty

False readings could mean some youngsters are still suffering. Picture: Getty

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Doctors are warning that allergies could be missed in children because many healthcare professionals are relying solely on blood or skin-prick tests.

Dr Kate Grimshaw, a specialist paediatric dietitian at Southampton Children’s Hospital, warned that not all allergies could be detected purely by measuring levels of a protein in the blood – immunoglobulin E (IgE) – which is linked to allergic reactions.

Just because a test is negative, the child may still be reacting

Dr Kate Grimshaw

Her advice follows new research into cow’s milk allergy, published online by the medical journal Allergy, which found that for every UK child who had a cow’s milk reaction due to IgE in their blood, there was a child who suffered a reaction who 
did not.

Dr Grimshaw, who was involved in the European Union- funded project known as Euro-Prevall, said: “We know that sometimes if a child is seen for a possible food allergic reaction – to any food, not just milk – but tests show there is no measurable IgE, then a possible food reaction may be ruled out when in fact the child may be reacting to the food, just not via IgE.

“This research will hopefully highlight to GPs and non-allergy specialists that just because an IgE test is negative, the child may in fact be reacting to a food and further investigations should be carried out.”

Food allergy reactions are split into two groups – IgE-mediated, which cause a range of immediate symptoms such as skin rashes, vomiting, respiratory issues and, in some cases, potentially life-threatening reactions, and non-IgE mediated.

Non-IgE mediated reactions occur around four to 28 hours after an incident and may cause stomach complaints such as diarrhoea or constipation, among other problems.

The study, which saw more than 9,000 babies from nine European countries followed up until the age of two, found that 1.3 per cent of UK children reacted to milk within two hours – the highest rate of all the countries involved – but only just under half (45 per cent) had IgE at a “high” level.

Professor Graham Roberts, a consultant in paediatric allergy and respiratory medicine at Southampton Children’s Hospital and principal investigator for the UK study, said: “Our study shows that a significant number of children can be reacting to a food despite having a negative IgE test.

“The take-away message for any non-allergy specialist is that if the patient’s history is convincing, then further investigations should be made if the IgE tests are negative, to ensure the child isn’t actually reacting to a food.”

The research, funded in the UK by the Food Standards Agency, was part of a project called Prevalence of Infant Food Allergy (Pifa), which assessed the development of food allergies in children in Hampshire in the first two years of life.

Dr Grimshaw and Prof Roberts now plan to reassess all 1,140 children who participated in that research at school age to discover what happens to allergies that started in early childhood, and find out which older children develop allergies and asthma.

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