Break out the Shampoo
One way to clean a helmet is to fill a basin or bathtub with warm water and a bit of mild liquid soap or no-tear shampoo. Using baby shampoo or something similar helps protect you in case some residue is left behind after cleaning and drips into your eyes. Dip a sponge in the water and use it to scrub the helmet, reaching into all the crevices and the plastic straps. Use a towel to remove excess water, and then leave it in a well-ventilated area to dry. To get rid of bacteria that resists an ordinary wash, regularly use a disinfectant spray or a diluted solution of bleach and water -- not more than 10 percent bleach to 90 percent water. Check the care tag before using the bleach to ensure it's not harmful to the helmet's lining.