Frostbitten toes are easy to identify. Immersion foot is not.
(this is another retread piece from June of '10. It is worth a few minutes of your time if my personal experience is any example.)
In the last couple of weeks I have been asking my buddies what they have been up to. With all the nasty weather over most of the Western states and into Canada no surprise many of us are still trying to ice/alpine or even "winter" climb of sorts.
Frost-bite is less of an issue outside of Alaska in spring. Immersion foot is not. And that injury is more serious than you might first think.
"Immersion foot occurs when feet are cold and damp while wearing constricting footwear. Unlike frostbite, immersion foot does not require freezing temperatures and can occur in temperatures up to 60° Fahrenheit (about 16° Celsius). The condition can occur with as little as twelve hours' exposure."
FWIW I suspect mild immersion foot injuries (the ones with no visual injury) are very common in the summer and winter alpine climbing communities but unreported and generally unrecognised for what they really are.
How easy is the injury to sustain? I came off a 24hr c2c winter climb and on the walk out decided I was tired enough a nap on the trail was in order. Something I had done before many times in the past winter or summer. I wasn't particularly dehydrated (but likely more than I realised), hungry or cold but with the early start from home, the drive, the approach, the climb, the decent and then the walk out I was pretty worn out and had by then been up for 30+ hrs. So a quick nap seemed a luxury. I laid down on my pack to keep me off the ground and figured as usual when the cold woke me up I'd finish the walk out with a bit more energy. The cold did wake me up as expected. So I got a 20 or 30 minute nap. And with in a few minutes of walking I was warm again and life seemed better. But what I hadn't noticed till then was I still had damp feet from breaking through some water ice earlier in the day. Took longer than expected while walking to the car for my feet to warm up, but they did eventually warm up. When I got home I took a hot shower and hit the sheets for a few hrs before I went back to work. When I finally stepped back into my shop I noticed the front half of both feet were numb. Because I kept climbing all winter it took a full 18 months for that to totally disappear and my feet are very susceptible to re injury. (front of my feet go numb) Now re injury can happen by just a few hrs of cold feet sitting at the computer early in the morning barefoot. Or wearing tight rock shoes in cool conditions and not moving, like a hanging belay for example, can do it as well.
Another example? I spent most of my first Alaskan expedition wiggling my toes every night for a hr or so before I fell asleep in my lwt bag if we weren't actually out climbing. I'd count the toe curls until I fell asleep. By the end of that trip I had numb toes but no frost bite injuries. I'd bet now I had a classic case of Immersion foot.
Not a lot is out there for the care of Immersion foot incurred in a climbing situation. Two friends I talked to about the injury said they had "frost nip", a third thought he had "nerve damage". But the symptoms are nearly the same. And almost everyone I know who has spent time out winter climbing has had either Immersion foot or Frost Bite. I suspect the basic treatment to heal the injury (nerve damage, Immersion foot, or moderate Frostbite-blisters) is also the same, keep your feet warm, clean and give yourself time to heal the injury completely without re injury.
What we miss is Immersion foot can easily lead to very serious re injury and less resistance to cold injuries in general.
So how do you know you have it? Many of us have always thought of it as "frost nip" but it generally is not. Immersion foot is serious damage to your nerves and circulation in the foot. And frost bite will be the freezing of tissue. But Immersion foot may have almost no outward sign of injury. Frost Bite most defiantly will. A good thing many of us are beginning to recognise there is an injury with Immersion foot by incorrectly naming it "frost nip". Your feet or at least the toes and forefoot become numb with Immersion foot. Get a good enough case of Immersion foot and even your once comfortable but tight rock shoes will now not fit and worse yet re injure you feet on a typical spring day and you don't have to have cold feet while it happens .
The other culprit that leads to Immersion foot is abuse, same reason the rock shoe scenario is so hard on their past winter's injury. Get on some hard and continuous alpine ice with a tight fitting boot and it is very easy to pound you feet and toes into submission with nerve damage. But sometimes it is hard to tell nerve damage from Immersion foot. Keeping your feet warm and dry once out of the mountains is your best chance of healing your feet quickly and getting back outside in comfort.
Besides making an effort to treat your feet better and wearing a warmer climbing boot this time of year with all the bad weather, what can you do once you have a good case of Immersion foot?
My answers to date: wear very warm shoes in the house or office so your feet sweat. Keep your feet dry even if you have to change socs several times a day while doing little or nothing. It will heal the nerve endings faster if your feet are warm. But avoid doing nothing once you are out of your boots. Walking seems to speed healing. Pounding out mileage I am not so sure about once you get into the "abuse of feet" distances. Watch how warm/dry your feet stay if you are riding a bicycle for training. Remember you only have to get to 60° Fahrenheit (about 16° Celsius) before damage can re occur. After the first incident with Immersion foot your feet will be damaged easier the next time. The amount of time between the first injury and the next exposure can make a difference as well on how you heal and your next case of Immersion foot. While your feet are still numb stay out of tight rock shoes. And most importantly avoid getting your feet cold again for any reason while they are still numb. The more time between exposures to cold the better.
As a side note to make the point. Have you ever heard of older people having "poor circulation" in their feet and them always being cold? Remember that Immersion foot can be experienced at 60° Fahrenheit. Many, many cases of "poor circulation" as we age are simply reoccurring Immersion foot events until the person has suffered permeate cold damage to their feet.
Make some one you know happy this winter (or all year long) by buying them chemical heat packs and show them how to put them in their slippers or sox :)