Mild soapy water, by hand, air-dried completely away from heat. That is the whole method, and the reason it is so restrictive is that a helmet has two liners: the removable fabric-and-foam comfort layer you can wash, and the expanded polystyrene shell underneath that manages impact energy and must never be soaked, scrubbed or exposed to solvents. Household cleaners, alcohol wipes, petrol-based degreasers and fabric softener all damage one or the other. The Snell Memorial Foundation's technical FAQ puts it in one line: use only mild soapy water on the inside pads, and never use chemical cleaning products inside or outside the helmet.
Two liners, two completely different rules
The comfort liner is what your skin touches: a moulded crown pad and two cheek pads, usually held in by press studs and plastic tongues that slide into slots. It is textile over soft foam, it absorbs sweat and sebum, it compresses over time, and it is designed to come out.
Under it sits the EPS — a rigid polystyrene shell, often in several densities, bonded or captive inside the outer shell. It does the actual protecting by crushing under impact. Water carried into the gap between EPS and shell does not dry out easily. Solvents attack both the polystyrene and, on a thermoplastic helmet, the polycarbonate shell itself, producing fine crazing that weakens the structure without looking like damage. MotoCAP's helmet care guidance lists the offenders directly: harsh cleaning chemicals, petroleum-based solvents, prolonged sunlight and excessive heat all speed up degradation of helmet materials "even though the damage may not be apparent visually".
So: the comfort liner gets washed, the EPS gets left alone, and the helmet never gets submerged. If your cleaning method involves a bucket and a helmet going into it, stop.
The routine that works
Before you pull anything out, photograph the inside. Cheek pads and crown liners go back exactly one way, the press studs are not symmetrical, and the ten seconds spent on a photo saves twenty minutes of puzzling later. Then work through it in order.
Remove the cheek pads first — they usually unclip downward and slide out past the strap — then the crown liner, which normally has studs at the front and a lip tucked under a trim strip at the rear. Some models route the intercom speaker wires through the pads; unplug rather than pull.
Wash by hand in lukewarm water with a mild soap or a plain baby shampoo. Squeeze the pads gently to move water through the foam. Do not wring them out: twisting shears the foam cells and permanently changes the pad thickness, which changes your fit. Rinse until the water runs clear, then press each pad flat between two towels and stand on it if you have to. Getting the bulk of the water out mechanically is what makes the drying time reasonable.
Dry flat, indoors, in moving air, for a full day. Not on a radiator, not in direct sun, not with a hairdryer — heat shrinks the foam and can distort the plastic mounting tabs. A fan pointed at the pads on a wire rack cuts the time roughly in half. Refit only when they are dry all the way through, because damp foam against EPS in a closed helmet is exactly how a helmet starts to smell.
Machine washing is a manufacturer-specific question. Some brands permit a cold, delicate cycle inside a mesh bag; many do not. Where it is allowed, skip the fabric softener — it coats the wicking fibres and destroys the very property you paid for, leaving a liner that feels soft and holds sweat against your skin.
| Part | Method | Frequency for daily riding | Never do this |
|---|---|---|---|
| Cheek and crown pads | Hand wash, mild soap, press dry, air dry flat 24 hours | Every 2–4 weeks | Wring, tumble dry, fabric softener, radiator |
| Non-removable liner | Damp cloth with dilute mild soap, blot, fan dry | Every 2–3 weeks | Soaking, submerging the helmet |
| EPS impact liner | Nothing beyond a dry brush of loose debris | Never washed | Any liquid, any solvent, any scrubbing |
| Chin strap webbing | Wipe with a damp cloth, air dry | Monthly | Bleach, soaking, machine washing |
| Visor and shell | Warm water, soft cloth, no pressure on the coating | Before every ride for the visor | Solvent cleaners, abrasive polish, paper towel |
Helmets with liners that do not come out
Budget helmets and some open-face models have the padding glued in. The method changes but the chemistry does not. Mix a small amount of mild soap into lukewarm water, wet a microfibre cloth, wring it nearly dry, and work over the padding section by section, blotting rather than rubbing. Follow with a second cloth wetted in plain water to lift the soap out. Then stand the helmet in front of a fan overnight with the visor open.
What you must not do is run water into the helmet to rinse it, or spray anything alcohol-based inside. The alcohol will get through the fabric to the EPS, and you have no way to inspect the result.
Why helmets smell, and what actually stops it
The smell is bacteria metabolising sweat and skin oil in a warm, dark, poorly ventilated space. Perfumed sprays add a second smell on top of the first and leave residue in the fabric. The three things that genuinely work are all about removing the conditions rather than the odour.
Dry the helmet after every ride. Take it off, open every vent and the visor, and leave it somewhere with moving air for an hour before it goes in the bag. Zipping a damp helmet into a padded bag at the end of a wet commute is the single most reliable way to grow something in it.
Wear a thin wicking balaclava or skull cap. It moves the sweat interface off the liner and onto something you can wash daily in thirty seconds, and it also protects the liner from hair product, which is a significant contributor that riders rarely connect. Leave-in conditioner and styling wax transfer straight into the crown pad and stay there.
And run two sets of cheek pads if you ride daily. They are inexpensive relative to the helmet, they let one set dry properly while the other is in use, and having a slightly thicker and slightly thinner set is a legitimate way to fine-tune fit as pads age.
Skin, fit and the point where cleaning stops helping
Friction plus occlusion plus sweat is a recipe for blocked follicles, and riders who develop spots along the forehead and jawline where the pads sit are usually looking at a hygiene-and-friction problem rather than a diet one. A clean liner, a fresh balaclava and drying the helmet after every ride resolve most of it. If it persists, that is a conversation for a doctor, not a gear forum.
Fit is the other thing a liner controls. Comfort padding compresses with use — that is normal and expected — but the effect is a helmet that slowly gets looser without any single day where you notice. Re-run the fit checks every few months: rotate the helmet and confirm your skin moves with it, tilt it forwards and back, then have someone try to roll it off the back of your head with the strap fastened. When a helmet that used to pass starts to fail, new pads are the fix, and they are sold per model in several thicknesses.
There is a point where no amount of cleaning is the right answer. MotoCAP puts a helmet's working life at around five years, or three with regular use, and the case for replacement is covered in the guide to when to replace a motorcycle helmet. A helmet that has taken an impact goes regardless of how it looks, as set out in the guide to what to do after dropping or crashing a helmet.
The exterior and visor are a separate job with their own rules, covered in the guide to helmet cleaning and care. It is worth doing, and not only for appearance: the UK Highway Code's Rule 83 tells riders to check before every journey that the visor is clean and in good condition, and Rule 84 notes that scratched or poorly fitting eye protection limits your view, particularly in bright sunshine and after dark.
Where the helmet lives between rides matters as much as how you wash it. MotoCAP recommends storing it in a bag somewhere it cannot be dropped, chin strap facing down, on a hard surface. That also means not hanging it on a mirror or a bar end, which deforms the padding at the contact point and undoes the fit you have been maintaining. If your reason for leaving the helmet on the bike is that you need somewhere to keep a camera or navigation unit, mounting a bar-mounted riding system to the machine keeps the electronics with the bike and the helmet with you.
Frequently asked questions
Can I put helmet pads in the washing machine?
Only if the manufacturer says so, and then cold, on a delicate cycle, inside a mesh bag, with no fabric softener. Hand washing is safer for the foam and takes about the same time once you account for the drying.
How do I clean a helmet liner that will not come out?
Damp cloth, mild soap, blot section by section, then a second cloth with plain water to lift the soap. Dry it in front of a fan overnight with the vents and visor open. Never pour water into the helmet or spray alcohol-based cleaners inside.
What makes a helmet smell, and do deodorising sprays work?
Bacteria feeding on sweat and skin oil in a warm damp liner. Sprays mask the smell and leave residue. Airing the helmet after every ride, wearing a washable balaclava and drying the pads properly deal with the cause.
How often should I wash the liner?
For daily riding, every two to four weeks, more often in hot weather. For weekend use, every couple of months. If it smells before that, the problem is drying rather than washing frequency.
Can I use disinfectant or alcohol wipes inside my helmet?
No. Alcohol and household disinfectants reach the polystyrene liner and can attack a polycarbonate shell, producing crazing that weakens the helmet without being obvious. Mild soap and water is the only recommended interior cleaner.
