Hospital admissions for food allergies among children rose by 500% over the past two decades, but the problem has been exaggerated by parents using unreliable testing kits available on the internet, the NHS watchdog said.
Between 6% and 8% of children under three in Europe and North America now have food allergies that can, in some cases, lead to severe reactions.
In response to the growing problem, the National Institute for Health and Clinical Excellence (Nice) has issued its first guidelines on food allergies in children to help GPs to spot the signs and symptoms.
While acknowledging the rise of food allergies the draft guidance warns against do-it-yourself tests sold on the internet and offered by alternative practitioners. Tests including hair analysis and kinesiology can wrongly diagnose food allergies, leading to children being put on damaging diets lacking in nutrients, it says.
The guidance advises GPs on when to consider the possibility of a food allergy and when to carry out further testing.
Instances where doctors should investigate a possible food allergy include if a child suffers from a skin condition such as eczema or itchy rashes, sneezing or shortness of breath, gastro-intestinal problems such as vomiting, difficulty swallowing or constipation, or anaphylaxis (a severe, hyper-sensitive reaction).
Methods of diagnosis include removing the suspect food from the diet for a period of time and then reintroducing it, skin prick tests and blood tests to detect antibodies.
Among the most common foods causing allergic reactions are cow's milk, fish, shellfish, eggs, peanuts, sesame, soy, wheat and kiwi fruit.
Dr Judith Richardson, associate director of Nice's centre for clinical practice, said: "Food allergies in children are becoming more common, therefore it is important that there are appropriate, evidence-based approaches in treating those with this condition.
"Many of the symptoms are common to other conditions, so it's not always easy to identify and diagnose food allergy correctly.
"This will be the first evidence-based guideline on how health professionals and others who work with young children should diagnose and assess food allergies in children."
