Cold toes are a common problem in ski boots, and a most unpleasant way to spend your day on the mountain. There are many causes of cold and numb toes in ski boots. Luckily most of the time it is a problem that can be fixed.
FIT ISSUES IN YOUR SKI BOOTS
If you do your boots up too tight (see previous post on putting your boots on right) you can squash arteries and capillaries in your feet that will stop the blood getting to your toes. The most common one is across the top of your foot (the dorsalis pedis artery). So don't do the buckles across the top of your foot up too tight, just enough to keep them closed and seal the boot - a flick closed with your thumb is enough. Another area that can block blood flow is behind the inside ankle bone (the tibial artery). This is a more complicated cause and is usually because there is too much padding in that area.
If you've tried loosening the buckles across your foot and it's made no improvement, I suggest you get it checked by a good boot fitter.
Blood flow problems to the feet can range from something minor like you just feel the cold (more common in women who are quite slim), to Reynaud's disease and peripheral vascular disease (PVD), in which case issues can be quite serious and lead to nasty complications.
If you have a history of PVD or diabetic foot ulcerations, then putting your precious feet into hard shelled boots all day to ski may be a serious risk that you should really discuss with your health professional.
People with Reynaud's disease should make sure they have a well-fitted boot and ski orthotic to ensure the best blood flow to the foot is happening. Once this is done, then it is worth considering a boot heater.
WHAT SHOULD I DO?
Wear a thin, woollen or synthetic blend (not nylon or cotton!) sock designed for ski boots. Wearing thick socks in ski boots will actually make your foot colder. A ski boot liner is designed to absorb some of your perspiration and draw it up and out of the boot. A thick sock's fabric will just get squished in your boot and hold the wet sock against your skin. Wet socks will be less breathable and prevent the transfer of perspiration to the liner, making your foot wet and cold.
Make sure your boots are dried out overnight and at room temperature when you put them on. Putting your foot into a cold boot in the morning is just asking for a painful day. Keep your boots inside (not in the car), someplace warm and somewhere without too much moisture. If you're lucky enough to be staying somewhere with a boot cupboard then use that, but beware of boot dryers. They can be too hot and can flatten out and deform your ski orthotics, or heat the plastic shell up too much so that any boot expansions you may have had may go back to their original shape.
Get a ski orthotic or footbed for your boots. Until your foot is supported in the optimal position and is stabilised in the boot by a ski orthotic, no other boot changes will be very beneficial.Holding your foot in its best alignment will improve blood flow and reduced localised pressure, allowing your boot to hold you more effectively without pain or discomfort.
IT'S JUST DAM COLD!
If you've checked and addressed all of the above issues, then it's likely that you're just skiing somewhere amazing and it is incredibly cold. For these instances I recommend considering a boot heater, or a neoprene boot cover.
A boot heater is a battery-run gadget that has a heating element installed under the ball of your foot within your boots. It has a battery pack and a control panel that sit on the side of your boot, or if you want to get funky, you can get extension leads to hook it up on your waist belt. These tend to be great for those people who just get cold feet no matter what they do and need a bit of extra assistance to keep their extremities warm. I recommend Hotronics FootWarmers. Heated socks are improving and worth a look at now too.
My bootfitting mentor in Canada, back when I was a young and fresh 19 year old, swore by neoprene boot covers. They are no fuss, no batteries needed or forgetting to charge them. No wires that might get loose connections and no installation fee. As long as you put your feet into warm boots to start the day and put the covers on early, you're in for a joyful foot experience. They work by keeping the snow off your boot. Simple.
But the true secret to any cold feet issues is to not let them get cold in the first place. So warm socks and shoes around the house before you go skiing is a must.
QUICK RUN DOWN
Do your boots up right
Have a good ski orthotic/footbed made for your foot and ensure a well-fitting boot
Wear a thin, woollen or synthetic blend ski sock
Make sure your boots are dry and warm before you put them on
Done everything else right but still feeling the cold? Consider a boot heater or neoprene cover
If you have serious blood circulation issues, discuss this with your health professional before skiing