Over thousands of years, peoples' feet have been protected and covered more and more to prevent injuries and allow us to be on our feet for longer periods of time on various types of terrain. While this means that we are protected more often, it makes our feet more susceptible to injury when they are not protected or are under protected. Thermal injuries can be related to both heat and cold and here we will discuss what these injuries are and exactly why they occur.
Being that it is July, let's get the talk about cold-related injuries out of the way first. Cold injuries to the body are named based on severity and include frost bite and frost nip. Frost nip is essentially a milder form of cold injury to the skin. There is ice formation in the tissues of the affected body part, but this is not severe enough to cause detrimental damage to the tissue. Effects of frost nip include pale appearance of skin and tingling and or numbness of the affected body part, which typically resolves after the body part is warmed.
Frost bite is graded in 4 degrees, depending upon the depth of tissue damage that occurs as a result of cold exposure. Factors that account for the damage to tissue include not only the external temperature, but also windspeed and moisture - and most importantly the time of exposure. Increased windspeed removes the protective warm layer of air from around the body part and when tissues or clothing are wet, they draw heat away from the body. If a person recognizes signs of early tissue cooling and seeks shelter and warmth, damage is minimized. In those who are unable to reach shelter or do not seek it, further damage occurs leading to loss of tissue and sometimes loss of limb. In 2nd, 3rd and 4th degree frost bite, blistering appears in addition to numbness and color changes. In 3rd degree frost bite, these blisters are blood filled and after re-warming, these blisters dry up and appear as eschar (black dry, scab-looking lesion). 4th degree frost bite leads to damage beyond the skin and extends to the muscles, tendons, nerves and bone.
Feet in the midwest should be well protected from the sun, as our feet are covered 1/2 of the year or more and are more susceptible to sunburn. Sun burn is the result of skin being exposed to UVA and UVB rays from the sun. Sundburn is not caused by the heat of the sun itself. Rather, over time, these rays actually damage DNA. This leads to superficial blood vessels dilating (opening up) and leads to more blood flow and inflammations. This is why sunburn isn't fully realized until hours after sun exposure. While the body can repair damaged DNA, repeated sunburns and sun exposure can make this more difficult and thus lead to the development of cancer. Slathering on sunscreen (SPF 30) and re-applying as directed prevents sunburn and sun damage. Also, make sure your sunscreen isn't expired. While there are some SPF 100 available out there, the verdict is still out on whether the chemicals in this strength of SPF are more damaging to the skin than the sun itself, so I tend to stick to 30 or 50.
Burns caused by fire or dropping hot liquids onto the foot are not something to be neglected. There are four degrees of burns. 1st degree burns (depending upon the extent) can be treated safely at home. These burns do not express blistering. 2nd degree burns are divided into partial or full thickness. In partial thickness burns, blistering appears with pink or red appearing skin which can look wet while full thickness looks red and dry. If you think you have a 2nd degree burn, it is important to seek immediate attention, as full thickness 2nd degree burns can require grafting to fully heal. 3rd degree burns mean that all layers of skin have been destroyed and appear black or white, dry and leathery and are not painful (due to nerves in the skin also being destroyed). These and 4th degree burns (damage extends to muscle and bone) require medical treatment as well. Burns that result in loss of skin cause dehydration among other things.
If you experience a thermal injury that does not resolve or improve within a couple of days, seek medical attention. Prevention is key, so wear sunscreen, avoid fires and extreme cold and bundle up when you know that the wind and temperature have created a risky situation outside!