Icing sugar can sometimes include wheat starch or cornstarch to keep the sugar soft and powdery, and so may not be suitable for coeliacs – check the packaging carefully before buying. Specialist bake shops may stock starch-free 'pure' icing sugar – as such, it may be lumpy and will require extra sifting before use. Pure icing sugar is preferred for making royal icing as the result will keep its shape better when piped or moulded.
