A recent cold blast that engulfed parts of the U.S., sending a bomb-cyclone up the East Coast and registering record-breaking temperatures from New England to North Carolina, killed at least 22 people and threatened millions of Americans last week.

While warmer weather is on the way, winter’s end isn’t for another three months. And with the expected chill, welcomes the chance for the season’s most significant risk – frostbite.

According to Dr. David Heller, emergency medical director at Portsmouth Regional Hospital in New Hampshire – less than two hours from Mount Washington Observatory, one of the coldest places on the planet last Saturday (minus 37 degrees with a wind chill of minus 93) – their emergency room sees a slow, steady trickle of frostbite throughout the winter.

“It’s been crazy cold here for the last couple of weeks,” said Dr. Heller, who also notes that it’s been cold everywhere, even Tallahassee, which had snow. “Because there were a lot of measures taken by the municipalities to make sure the real at-risk people were protected, we did not see as much frostbite as we might normally see, thankfully.”

It was about 30 degrees in New Hampshire when we spoke with him – “warm” compared to what they’ve been experiencing – and he explained that those temps are when you might see frostbite.

“People are out walking their dogs and doing things, and, if you don’t pay attention and you’re out for too long and your skin is exposed during that time, this is when you could get frostbite,” he says.

Dr. Heller answered more frostbite-related questions and gave advice on how to protect yourself below.

What is frostbite?

In the simplest terms, frostbite is when your skin tissue freezes. It’s freezing of the tissue that make up your skin, on the exposed part, and when your tissues freeze, it can release certain chemicals in your body that actually cause the skin to become damaged. Frostbite is the damage from that freezing process.

How long does it take for someone to get frostbite?

It varies. It depends on the temperature, the duration of the exposure, and the person’s underlying health. It also depends on things like wind or whether you are wet or dry.

For example, normally, if you have a wind chill of 18 degrees below zero, which we’ve had fairly persistently over the last couple of weeks in New Hampshire, you can get frostbite in 30 minutes. But if the wind chill gets down to 32 degrees below zero, you can get frostbite in 10 minutes; with a wind chill of 48 degrees below, you can get frostbite in under five minutes.

In the last couple of weeks, people really needed to make sure they weren’t exposed for very long, otherwise they would get frostbite.

What are some ways to prevent frostbite?

The easiest ways to prevent frostbite is to not get exposed to the cold; stay inside. If you have to be outside and exposed, then you really have to dress in layers, try very hard not to get wet and make sure that any kind of exposed skin is covered. And when I say covered, I mean some type of clothing. There are creams and protective lotions that are advertised to put on your skin, but they have not been shown to really protect you from frostbite.

How do you recognize frostbite?

It’s like a burn – there’s mild, moderate, and severe.

Mild: In the early stages of a mild frostbite, you may see a little redness and swelling. Usually, you’ll have some kind of stinging or burning that might start throbbing later on. You may also see sloughing of the skin, not anything to be concerned about. You typically don’t see blisters at this stage.

Moderate: If it’s involving deeper tissues or a more wide spread injury to the skin, that would be considered second degree frostbite. Usually, you’ll see some fairly significant swelling, redness and clear blisters that will form within 6-24 hours, on average. You may have some numbness, at first, with aching; but later on, it will become more of a throbbing sensation and, in the next 1-2 days, you will start to see more sloughing of the skin and a blackish hue to the skin as well.

Severe: This stage would be third degree and that’s when there’s significant freezing that goes through all of the layers of the skin and even below the skin, the sub-dermal area, which also will get damaged. In this stage, you form what’s called hemorrhagic blisters, and if you pop these blisters, there wouldn’t be clear fluid, you would see more of a bloody fluid. The skin will typically turn a bluish/gray color with this degree of frostbite. Also, people will describe their skin feeling weird…like a block of wood. With severe frostbite, you will sense a fair amount of burning, throbbing and shooting pains. At this stage, your chance of complete recovery is not all that high.

In the lesser stages of frostbite, if you are a relatively healthy person, in time, you will recover. There’s even a fourth stage of really, severe frostbite where it not only involves the skin, but it goes down into your muscle, bones and tendons and that’s when your skin will turn very black and thickened. There will be some deep aching in your joints and, for that, the prognosis is very poor and most people usually have some sort of removal of that tissue, which would mean an amputation (see Everest blog).

Who is most at risk?

People who have general poor health are much more prone to frostbite because they don’t have the mechanism of keeping their body warm that healthier people do.

  • Diabetics are more prone to frostbite;
  • People who smoke (smoking impairs your circulation, which makes one more susceptible to frostbite);
  • People who have poor circulation, in general;
  • The elderly and people with limited social assistance, such as poor or homeless people;
  • People who are under the influence of drugs or alcohol are much more likely to make a poor decision and not recognize that they’re being exposed to the cold;
  • Psychiatric patients are also at-risk.

What areas of the body are most commonly affected?

The feet, hands and face are the three areas that are usually exposed and most commonly affected. Your hands and feet are areas where the circulation isn’t as good as other parts of your body, so it’s harder to keep those areas warm. Also, your feet can be in tight boots and can get cold or wet and, of course, wetness is going to increase your chances of frostbite considerably. Your face does have good circulation, but your nose and ears – the most prone – are usually exposed.

What’s the best way to treat frostbite?

The best way is to get the person out of the cold as soon as possible and do rapid re-warming, which is usually performed in warm water between 104 and 107 degrees (the temperature you would find in a hot tub or Jacuzzi). If you’re out in the wilderness and cannot get to a warm area right away, it is recommended that you not warm them until you are in a definitive warm environment. If they are re-warmed and then refreeze, there’s actually worse damage being done. So, if you can get them to a warm place and rapidly warm them, that’s the easiest way to treat it and then you just have to monitor. In the initial stages, it’s very hard to know what degree of frostbite you have. It takes monitoring over a day or two to know if it’s first, second or third degree because it all starts out looking the same.

What are some complications of frostbite?

The main complication that we see are people who get frostbite, even though their frostbite has been treated and their skin is back to normal, continue to have sensitivity to cold. That could be permanent damage. We don’t understand why that is but it’s a very common complication.

You can also get an infection. If you don’t take good care of the frostbitten part, you can get an infection to the part on top of the frostbite, and now you’ve got two problems to deal with.

Lastly, if it’s not healing or if there’s permanent damage that is not regenerating, then you’re talking about having to amputate that particular part of the body.

What’s one thing people should know about frostbite?

If you’re planning on doing outdoor activities in a temperature that’s below freezing, you really need to not only look at the temperature, but you have to look at other factors, including:

  • wind,
  • whether you’re going to be in a wet environment; and
  • your general health – if you’re not a healthy person, you should think twice about exposing yourself to the weather.

You also need to really dress in layers and be cognizant of how long you’re going to be outside and exposed to bad elements. As long as you’re vigilant about that, you can minimize your risk. It’s when people drink alcohol, for example, and their judgement gets impaired, that they get into trouble. Vigilance is really the key to your safety.

Dr. David Heller is a board-certified emergency physician and emergency department medical director at Portsmouth Regional Hospital, an affiliate of HCA Healthcare, and its freestanding emergency room in Seabrook, N.H.