A review in the Drug and Therapeutics Bulletin (DTB) said NICE was wrong to recommend cream with a sun protection factor (SPF) of 15.
NICE guidance says SPF15 cream 'should be sufficient' to prevent sunburn if adequately applied. The researchers found this assumed cream was being applied at 2mg/cm2. People usually apply much less than this.
Evidence showed that SPF50 sun cream applied at 1mg/cm2 only afforded the same protection as SPF7 cream.
To follow NICE advice, an adult would need 35ml of cream per application. If applied every two hours, as NICE advises, a 200ml bottle would be required every two to three days. The journal argued this was 'impractical' and the way creams are assessed should reflect their actual use.
It added: 'Products labelled with an SPF of 30 ... will more reliably deliver adequate protection to most people and would be sufficient to prevent sunburn under most circumstances. We believe this is what NICE should have recommended.'
Are the findings significant?
DTB editor Dr Ike Iheanacho said: 'In DTB's view, NICE's recommendation overlooks the key evidence and is not in the best interests of public health. This advice needs urgent review.'
The journal advises people to apply SPF30 cream to exposed areas and to reapply after swimming or sweating. Fair-skinned people should go out in the sun without cream for 15 minutes two or three times a week to ensure adequate vitamin D levels, however.
Professor Mike Kelly, director of the NICE centre for public health excellence, said NICE's guidance did not seek to propose the optimal SPF to use. It was meant to advise the most effective way to reduce skin cancer risk in England. Professor Kelly said an expert report commissioned as part of its review recommended SPF30 'to take account of people not applying sufficient quantities' of sun cream.