There is no scientific evidence that complementary therapies or kits sold through websites can identify allergies, the NHS watchdog NICE says. It says sites for services such as hair analysis use plausible stories but are not backed up by scientific evidence.
It is publishing new guidance to help doctors in England and Wales identify when a child may have allergy problems. NICE says some parents end up turning to alternative therapies after a perceived lack of help from their GPs. It is estimated that one in 20 young children has a food allergy.
Dr Adam Fox, an allergy specialist based at the Evelina Children's Hospital in London, says not all children suffer immediate and obvious symptoms.
"Food allergies can actually be extremely subtle. Lots of children have eczema, colic or spit up more food than usual. For some of those children the underlying problem is an allergy to something within their diet."