We would recommend using a soft cloth with neutral soap and warm water, rinse by wiping with a soft wet cloth. When you have finished, turn the helmet upside down so that any excess water can drain out of the air vents and leave it to dry at room temperature and well away from any sources of heat (sun, radiators etc...).
Do not use gasoline, benzene or other chemical products and solvents; these may damage the helmet and affect the functioning and structure of some of the parts, and weaken the protective features