The most traditional duvet filling is down, which is lightweight and retains heat well. However, down duvets can lead to overheating, so some people prefer synthetic fibres, which tend to be more breathable and easy to wash. Or you might opt for a duvet made with other natural materials, such as wool, bamboo or silk. For more on this, read our article on how to choose the right duvet filling. There are also some stuffings that can worsen allergy symptoms, so head to our guide to duvets for allergies for info on that.