Don't put your bicycle helmet in a dishwasher!
Summary: Dishwashers damage bike helmets. Clean your helmet as recommended by the manufacturer, or just use mild soap and water.
But parents who are in a hurry sometimes dump the kids' helmets in a dishwasher. We don't recommend that.
We washed a selection of helmets in two dishwashers. We used the top rack in the one with an exposed heating coil.
The results were not good. Some helmets were ruined:
Labels are importantThe stickers inside a helmet are important. Washing labels out of a helmet means you or the next user will have not know what standard the manufacturer has certified that the helmet meets. That means you can't verify the helmet's age or if a more recent standard ensures better performance. It also prevents identifying a recalled helmet to return.
Impact PerformanceAfter the washing treatments were finished BHSI shipped some of the helmets with apparent degradation to the accredited independent testing laboratory at Southern Impact Research Center to determine if the washings affected the helmets' performance. The lab tested the straps, then impact performance with impacts on the flat anvil at 6.2 m/s, corresponding to the flat anvil drop of the CPSC bicycle helmet standard.
The lab test results showed that even the most apparently affected helmets still met the basic flat anvil impact requirement of the CPSC impact standard. That included models with taped-on and glued-on shells that had warped or even detached. The Giro model had identical performance to earlier testing of unwashed samples.
Other machinesDishwashers ruin helmets, with only water spray and heat. A washing machine tumbles or agitates the laundry, and is so likely to damage a helmet's impact performance that we will not even test with one. Microwaves will melt the foam and plastic shell. Hand cleaning takes only a few minutes and will not damage your helmet.
ConclusionNever put your helmet in a washing machine, dryer, microwave or dishwasher to clean it!
Testing DetailWe have a detailed writeup with more photos.
This page was revised on: October 29, 2020.