Despite its outward simplicity, a helmet is a complex collection of materials designed to keep you safe in a crash. Keeping all of them clean means using the right cleaners for the job.
The outside of a helmet, the shell, is what collects the most dirt, thanks to road debris and flying insects. Crusted-on bug guts should first be softened up by draping a wet paper towel or two over the helmet. Give the water 15 minutes or so to moisten the bugs, then use your fingernail to remove the largest and most stubborn. If you go straight at the shell with a cleaner and a rag you run the risk of tiny abrasive dirt particles scratching the finish.
The same goes for the face shield, on which scratches are more than just a bother, they’re a hazard. Use either warm water and a mild soap or a cleaner made specifically for clear plastic. If the shield has an anti-fog insert like a Pinlock, use only soap and water on it because cleaners, even those designed for clear plastic, can damage the thin anti-fog coating on the insert.
Avoid using any cleaners on the shell or shield that contain ammonia or solvents of any kind. If the bottle or can doesn’t say it’s safe to use on a helmet, don’t. Harsh chemicals in common cleaners can attack the shell and weaken it, or dull the finish of the graphics. Apply the cleaner to a rag, and then use it on the helmet. Don’t spray the cleaner directly on the helmet because it gets into the vents and shield mechanisms where it builds up and collects dirt.
Inside the helmet, the layer of padding closest to your head is called the comfort liner. Most recent helmets have removable comfort liners so you can wash away the accumulated sweat and skin oils that not only smell bad after a while, but can eat away at the comfort liner itself and eventually even attack the vital EPS liner. Remove the comfort liner and wash it by hand in warm water and mild soap like Woolite or baby shampoo. Rinse it thoroughly, at least a couple of times more than you think is necessary, to remove all the soap. If you don’t get it all out, the next time you ride on a hot day your sweat can mix with the soap and run down into your eyes, where it will sting.
Helmets with non-removable liners can usually be freshened up with sprays and cleaners made for this purpose. Some are anti-microbial to kill mold and bacteria that grow in warm, dark, humid places and make the inside of your helmet smell like an old sock. When they’re really filthy, helmets with non-removable liners can often be washed in a bucket or tub, but check with the manufacturer. Never use a heat source such as a hair or clothes dryer to dry helmet components.
Most helmet manufacturers recommend a complete cleaning inside and out once a year, with touch-ups in between as needed. It’s also a good idea to clean your helmet right before you hang it up for the winter so you’re ready to ride as soon as the weather turns in the spring.