Maintenance of Cycle Helmets
How to clean your helmet is usually in the manufacturer's instructions, if not, you can check the manufacturer's web site. Helmet can be immersed in water and still perform, but do not leave it immersed for too long as the materials will absorb some water that may affect the adhesives used in construction. In addition, foam saturated in water usually gives a harder landing on flat surfaces. The usual instructions for cleaning a helmet call for washing it in mild soap and water, rinsing thoroughly, and air drying. We normally use a few drops of dish-washing liquid in a bucket of water and a sponge. If you take a shower, you may wash it there too. Never use solvents or harsh cleaning materials on your helmet, since some of them may attack the foam or the shell and weaken the helmet. Gasoline, for example, dissolves EPS foam so well that in some developing countries the resulting gunk is used as glue. We did a test of many commonly used consumer products for helmet damage and found that most of them did not cause performance degredation despite some visible effects. So never wash your helmet in a washing machine; dryer; dishwasher or microwave to clean it! As tests show how it will degrade your helmet. If you someone has worn your helmet and you suspect they may have head lice, then put the helmet in a plastic bag for two weeks until any nits left behind have hatched and died. See the cleaning products below or our page on lice for more solutions.
source - helmets.org
