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Children are being placed on restrictive and potentially dangerous diets as parents look to the internet and the high street for alternative tests to diagnose food allergy, NICE warns.

NICE has issued the first ever national guideline on food allergy in children which advises against the use of alternative tests, such as Vega testing, hair analysis and kinesiology.

The use of these alternative tests is on the increase because of a lack of allergy services on the NHS and difficulties with diagnosing the condition in primary care.

But there is very little evidence to support the use of these tests, some of which can retail for £60 or more.

It is estimated that of those children who report an allergy, 20 per cent wrongly self-report diagnoses of various food allergies and do not eat certain foods because they think they are allergic to them.

NICE recommends that GPs, practice nurses and health visitors diagnose and assess a suspected food allergy, commonly an allergy to cow's milk, fish and shellfish or peanuts, using either skin prick testing or by taking a blood test for IgE antibodies.

This decision should be based on the results of the allergy-focused clinical history and whether the test is suitable, safe and acceptable to the child.

Dr Adam Fox, Consultant in Paediatric Allergy at Guys and St Thomas' Hospital in London who was involved in the development of the NICE guideline, said: “These are the only two scientifically proven tests that should be carried out to diagnose food allergy, and they should be validated alongside a full clinical history.

“It is very frustrating when you see a patient who has had a bad deal. Parents often think that these alternative tests offer a quick fix but many children often end up on restrictive diets.

“I have had parents who have come to see me holding a printout based on a completely unvalidated test that they have bought from some shiny website.”

Dr Fox added that IGG testing, often confused by parents with the scientifically proven IgE blood test, is readily available on the internet but does not have a role to play in food allergy testing.

Dr Joanne Walsh, a GP who was also involved in the development of the guideline, said: “Parents want to do the best for their children so many will take up these alternative tests.

“This guideline will help to empower GPs to recognise the symptoms of food allergy, to take a really good history, and offer the most appropriate tests.

The guideline comes as the number of food allergies rises across the UK, with a 500 per cent increase in hospital admissions seen since 1990.

One in every 20 children will develop a food allergy, which means that every primary school year group is likely to have a child with an allergy.

“Many of us in primary care are seeing an increase in numbers. Just last week I saw 1 or 2 cases of food allergy in one surgery,” said Dr Walsh.

“The bulk of what I see in my clinic is now food allergy,” added Dr Fox.

“In the past we tended to see the immediate type of reaction, such as a reaction to nuts, but now we are seeing much more in the way of serious delayed reactions like colic or diarrhoea. We don't know why there has been such an increase.”

The hygiene hypothesis - where a lack of exposure in early childhood to infections increase susceptibility to allergies - has been suggested but this theory has holes in it, he said.