Disclosure statement Disclosure of potential conflict of interest: P. J. Turner declares grants from the UK Medical Research Council, the UK Food Standards Agency, the Jon Moulton Charity Trust, and the National Institute for Health and Care Research/Imperial Biomedical Research Centre outside the submitted work, as well as personal fees from the UK Food Standards Agency, UpToDate, Elsevier, ALK, and Allergenis outside the submitted work. The remaining author declares no relevant conflicts of interest.