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Allergies in children are on the rise. It's estimated that between 6 and 8 per cent of children under three in Europe and North America have a food allergy.

And the last two decades have seen a 500 per cent increase in hospital admissions for food allergies among the young.

In response to this growing problem, the National Institute for Health and Clinical Excellence (NICE) issued new guidelines in February on food allergies in children.

The guidelines should help GPs spot the symptoms of allergies, but they are also aimed at parents who may be misdiagnosing these allergies in their children.

We find out the best ways to test your kids for allergies, and we look at the pitfalls of DIY home kits.

DIY tests may be less than helpful. According to the NICE report, growing levels of misdiagnosis has, in part, been fuelled by use of home-testing kits now widely available on the internet and high street, as well as by complementary therapists offering a range of different tests.

If you're concerned your child may have a food allergy, how do you know these DIY tests are trustworthy?

And what about other options, such as VEGA testing, hair analysis or kinesiology, offered in alternative therapy clinics across the UK?

The NICE guidelines are unequivocal: only tests performed either by your GP, or a specialist allergy clinic, are reliable.

None of the DIY tests or methods offered by complementary therapists have any scientific validity whatsoever.

According to Dr Adam Fox, consultant paediatric allergist at Guy's and St Thomas's Hospital, London, these tests should be avoided – and in some cases, they may even be harmful for your child's health.

'Lots of our patients use them, but they can result in children being misdiagnosed and either excluding foods that aren't a problem or, more worryingly, continuing to eat foods that are detrimental to their health,' he says.

It's helpful to understand that, broadly speaking, there are two types of food allergy.

Dr Fox explains the difference. 'With immediate-type allergies, you see a reaction very quickly after you eat the food, usually within a few minutes.

'Symptoms include hives, itchiness and swelling – and, if you're very unlucky, those reactions can cause anaphylaxis, a potentially life-threatening allergic reaction.

'Delayed-type allergies are more subtle and harder to spot, because it's the chronic build-up of a particular food that causes the allergic reaction.'

In young children, the most common delayed-type allergy is to milk protein, which causes chronic symptoms such as eczema, reflux, colic and diarrhoea.

This is not to be confused with lactose intolerance, which does not involve the immune system.

Delayed-type allergies are difficult for doctors to diagnose, partly because there's no obvious relationship between eating the food and the onset of symptoms.

The fact that these symptoms are also common in children without allergies makes a diagnosis harder still.

According to Dr Fox, the new NICE guidelines – which he helped draw up – will make this diagnosis easier.

'With our new guidelines, your GP is encouraged to take an allergy-focused clinical history,' he says.

'He or she should ask the right sort of questions, which will make it clearer whether your child has an allergy or not and, if so, whether it's immediate or delayed. And on the basis of that, they can decide which tests are appropriate.'

For an immediate-type allergy – commonly caused by milk, egg, peanuts and other nuts – the validated tests are skin prick tests and a specific IgE (immunoglobulin E) blood test.

If your GP doesn't have expertise in this area, they will refer you to a specialist clinic like Dr Fox's, which will administer the tests.

For delayed-type allergies, testing is less straightforward.

'The only test, which is helpful, is to cut out the food you think is causing the problem for a few weeks and then reintroduce it,' says Dr Fox.

'This is called an exclusion diet, and if the symptoms get better without the food and worse when it's eaten again, you can diagnose the allergy.'

Like the skin prick and blood tests, this should only be administered by your GP or at a specialist allergy clinic – given that you're testing for a potentially life-threatening condition, the importance of this is clear.

The NICE guidelines, including a parents' guide on what you should expect from the health service, are available via the NICE website.

It seems clear that, if you're concerned about your child, the first port of call should be your GP – and not one of the many unproven and often unhelpful alternative tests on the market.

Food intolerance is an adverse reaction to a particular food or ingredient, which occurs every time the food is eaten.

It's often confused with a food allergy, but it's very different because the immune system isn't activated.

Instead, food intolerance occurs when the body is unable to deal with a certain foodstuff, usually because it doesn't produce enough of the chemical or enzyme needed to properly digest that particular food.

One of the most common intolerances is to cow's milk, which contains a certain type of sugar called lactose.

If you have a shortage of the enzyme lactase, you can't break down milk sugar into simpler forms that can be absorbed into the bloodstream.

If your child is intolerant to lactose and eats or drinks dairy products, they may experience symptoms such as bloating, abdominal pain and diarrhoea.