Conflicts of interest: A.A. reports ad hoc consultancy for AbbVie, Almirall, Emma Hardie, Garnier, LEO Pharma, L’Oréal, Proctor & Gamble, Neutrogena, Nivea, Novartis, Prai Beauty, Revive Collagen, Sanofi, The Body Shop, UCB and Unilever; has held a position of interest for the Trial Generation and Prioritisation Panel (UK Dermatology Clinical Trials Network); and is an Executive Committee Member Psychodermatology UK and the British Association of Dermatologists. L.F. has received honoraria from La Roche Posay for participation in an advisory board. T.W.G. is named on the Walgreen-Boots academic grant via the University of Manchester; is a trustee of the British Association of Dermatologists, the British Skin Foundation and the Cosmetic Practice Standards Authority; is a director of the skincare company CGskin in collaboration with the University of Manchester (not currently trading); and has received honoraria within the past 3 years (for teaching and advisory boards) from Allergan and L’Oréal.