"For patients with oily skin, I will always suggest sticking to a treatment moisturiser that has mandelic acid in its formulation," says Pamela Marshall, clinical aesthetician at Mortar and Milk in London. This is because the hydration will help to control oil production and the mandelic acid will help to decongest the pores. For oily and acne-prone skin, Marshall suggests Exuviance Night Renewal Hydragel (£42).