But checking levels involves a painful finger-prick test, which deters many from carrying out the test.

BBC: Pain 'prevents diabetics checking health'

Half the cuddled babies did not show any facial expression of pain when undergoing a heel prick test.

BBC: Premature babies 'need cuddles'

At age four, they were also given a skin-prick test to see if they had any of the most common allergies, including dust mite, animal fur, pollen, milk, eggs or peanuts.

BBC: Doctors could predict which children are at risk of asthma