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Previously: Feet

Skin
As hikers, we must protect our skin from the environment. We can wash by showering in towns and swimming in lakes. Hair follicle infections will be minimized if we keep clean, and cuts and scrapes will be less likely to become infected. We can wear long sleeve shirts and long pants to protect against sunburn, scrapes, and poison oak and ivy when appropriate. We can inspect our skin regularly to discover problems early, and we can address any problems we have.

Skin Problems on Feet
Skin problems on feet are discussed in the chapter on feet.

Sun Burn
A sunburn is a radiation burn from the sun. General damage to skin cells kills them in the short term, and in the long term, radiation damage to the DNA of the skin cells that survived may cause skin cancer.

Hikers can limit sunburn by wearing big hats, long sleeved shirts, and long pants, or applying sunscreen, or resting in the shade, when the sun is brightest. Long clothing, however, tugs against us when hiking and holds in the heat from exercise. Sunscreen accumulates dust and is itself a layer of gunk on the skin. Dirty skin may cause infections and rashes. And finally, we don't get from Mexico to Canada by sitting around in the shade. So like every other issue, we must understand the big picture and make our choices carefully.

Some of the light produced by the sun is blocked by the air in the atmosphere. The more air the sun passes through, the more UV light is blocked. The sun passes through the least amount of air at high noon and on the equator because it shines straight down through the atmosphere layer. Earlier or later in the day, or further from the equator, the sun shines diagonally through the atmosphere. Therefore it passes through more air, and more UV is blocked. At higher altitudes, there is less air and less protection above us. By resting in the shade near noon, and by being more careful in the southern ends of our hikes and high altitudes, we can limit UV exposure.

Snow, water, and white soils reflect sun back up on our bodies, increasing the dose on each bit of exposed skin. Also, the reflected light may shine up your shorts and nose, onto the roof of your mouth, and on other areas that normally receive little light. Since they've never been tanned, they may burn quickly. Long pants and bandannas over the face may be a good idea on long snow traverses.

Sunburn is caused by UV-B and UV-C. In the short term, both UV-B and UV-C damage the skin cells enough to kill them. And in the long term, the damage they cause to DNA can lead to mutations and cancer. UV-C from the sun is blocked by the atmosphere, but sources that are near us, such as UV-C water sterilizers and Arc Welders, can burn us.

UV-A ages the skin cells, by damaging elastic fibers and thickening the skin, and by causing DNA mutations. But UV-A does not cause sunburn.

Effect on DNA and RNA
In DNA, where two thymine bases are adjacent, ultraviolet light may cause a covalent bond to be made between the two thymine bases. This produces thymine dimers, which destroys the ability to use the information stored in the DNA. RNA does not contain thymine, and uracil-uracil and cytosine-cytosine dimers are formed. UV causes other nucleic acid flaws at much lower frequencies.

The body recognizes this nucleic acid damage and attempts to repair it. Not all damage gets repaired, and nucleic acid damage may lead to skin cancers: melanoma, basal-cell carcinoma and squamous cell carcinoma. Melanoma risk increases with each sunburn episode.

Tanning
Also as a result of UV nucleic acid damage, the skin cells increase production of Melanin. Melanin is the brown stuff of skin tans and darker skin tones. And since melanin absorbs UV light, it protects other parts of skin cells from UV damage. So getting a tan trades some extra exposure to the sun early for some extra protection later. Hikers should recognize that when the weather gets hot, and we start shedding long sleeves and pants, etcetera, untanned skin is likely to burn much more quickly than that which was already exposed and tanned. We should carefully monitor untanned skin and make sure we limit exposure to prevent burns. Finally, tanned skin only reduces danger, it does not eliminate damage. Even tanned skin should be protected by shade, clothing, and sunscreen.

Level of Burning
In less than 15 minutes, a sunburn can occur. (Arc welding and other artificial UV sources can burn in seconds.)

In a minor burn, the skin reddens (erythema) after a half hour to 6 hours. Pain appears with the redness, and is most intense for a couple of days. The burn may worsen for three days, and sometimes enough of the skin is killed that a dead layer peels off over the next week.

More serious burns may involve blisters, rashes, itching, nausea, fevers, and chills.

Certain medications may increase the chances of sunburn, such as some antibiotics, oral contraceptives, and tranquillizers.

Eyes can also be burned by the sun, causing snow blindness in the short term, and in the long term, macular degeneration, pterygium and cataracts.

Cold Injuries
Frostnip and frostbite are damage from freezing of tissue.

Ears are subject to frostbite because they are thin and have little blood flow.

Feet, legs, hands, and arms are often less insulated by clothes than the core of the body. Therefore, cold winds are able to chill them faster than the body. They are also smaller in volume. A finger, for example, freezes faster than the body because the body has a huge amount of warm organs that supplies heat to the skin, where no such large heat reservoir protects the finger.

Furthermore, when the body core begins to fall in temperature, one response is to start to cut off blood flow to skin so that the skin won't radiate body heat out to the cold environment. This results in a whiter, bluer skin tone than normal, and makes it much easier to freeze the skin. If limiting blood flow to the skin isn't enough, blood flow to the arms and legs is restricted. With less blood flow, the arms and legs chill faster and are more subject to frostbite.

Avoiding frostbite involves keeping the body warm by wearing enough warm clothes, by eating enough calories to keep heat production up, and by drinking enough water to keep the blood flowing to the extremities. Hats are important because there is a great deal of blood flow to the head and little natural insulation. A good hat can keep your whole body warmer. The hat also ought to cover your ears. Good gloves, boots, and socks are important. If the boots are tight enough that they cut off any circulation, that promotes frostbite. Finally, the body trunk must be kept warm if it is to supply enough heat for the extremities. If a hiker can't keep warm out hiking, it may be best to stay in the shelter of the tent and the insulation of the sleeping bag, or in a hotel room in town.

First Degree Frostbite
First degree frostbite is the most superficial and is sometimes called frostnip. In frostnip, only the outermost layer of the skin freezes. Most of the skin cells revive after thawing. The skin damage cases pain, itching, and red, white, or yellow discoloration. Long term insensitivity to heat or cold can result.

Second Degree Frostbite
Second degree frostbite involves the freezing of the full thickness of the skin, but not the freezing of the underlying tissues. Blisters may occur 1-2 days after thawing, and the skin may harden and blacken. This level of skin damage probably would end a long distance hike, because of the pain and the difficulty of keeping the skin warm, dry, and clean to allow healing.

Third and Fourth Degree Frostbite
The underlying muscles, tendons, blood vessels, and nerves freeze solid. The skin is hard and waxy. The long distance hike is over, and the new challenge is getting to a hospital while doing as little additional damage as possible. If there is any chance that the part will freeze again, it may not be wise to thaw it, as each time ice forms, damage occurs to the cells and structures.

Rewarming of any frostbitten area should be done carefully because the frozen area may not feel heat. If the area were exposed to a campfire, for example, it could burn without the person feeling it. Warming less aggressively, say by holding the frozen part under the jacket on the warm skin of the trunk, may be better.

Poison Oak and Ivy
Poison Oak is common in wetter areas of the western US. In the eastern US, Poison Ivy is common. Poison Oak and Ivy have three leaf clusters. The middle of the three leaves has a bit of stem between the base of the leaf and the junction of the three leaves. Sometimes poison oak and ivy grow up trees as a vine. The vine has a hairy covering of roots growing into the air. Other times, poison oak and ivy grow as a bush.

Poison Sumac grows in Florida and has 7 - 13 untoothed leaflets. It is a tree that can grow 6 - 23 feet tall.

All of these plants have Urushiol, a powerful allergen. This oil adheres to your skin and to anything else, such as your clothes or gear, or your dog. Touching these later can transfer some urushiol to your skin. Some oil can rub on as you lightly brush past a leaf, much more oil if you're doing heavy bushwhacking, breaking branches, or getting scratched. The first line of defense is to recognize the plant and avoid touching it. Failing that, much of the oil can be removed with soap and water or by rubbing in some other oil and then washing that off with soap.

Once the urushiol has been washed off, the rash can't spread to another person. However, since the rash is an allergic reaction, it can spread to other parts of the body of the victim after the urushiol has been washed off.

Rashes appear in about a day, may worsen for several days, and typically persist for a week or two. The rash may include redness, swelling, blisters, and streaking.

Since the rash is an allergic reaction, repeated exposures may result in progressively worse symptoms.

Sensitivity to urushiol varies from person to person, and over time for a person. Some exposures to urushiol cause no reactions at all, while others cause severe reactions.

Poodle Dog Bush
Poodle-dog bush, Common turricula, or Turricula parryi is of concern along the Pacific Crest Trail in the chaparral lands of southern California. Its seeds can remain dormant for many years. After a wild fire or a soil disturbance, conditions are ideal for its growth. It can then persist for years until other plants return and out compete it. It can grow in large communities, invading long sections of trail. It may have pretty blue - purple bell shaped flowers from June to August. It has an offensive stink.

It can cause skin irritation including blisters lasting about two weeks. Some reactions have required hospitalization.

The key to avoiding poodle-dog bush is to understand what recently burned lands look like, and within those areas, to look for and avoid touching the plant. Lists of known areas are available online and from trail angels, but they are incomplete, and the observant hiker will find more plants and communities.

Skin Friction Rash
Often a rash may form where two pieces of skin or skin and clothing rub together.

The problem is worsened if the skin is damp. Getting more ventilation to the area may dry the skin and help some. Or stopping occasionally to ventilate and dry the area may work. Taking off some clothing or hiking in a cooler part of the day may allow you to keep walking while sweating less.

Dirt, skin oils, or even poison oak / ivy toxins may be exacerbating the skin rash. Stopping to wash your skin and the clothing that is touching the sensitive area may help.

The problem may be related to a specific piece of clothing. Perhaps a seam or fold is rubbing the sensitive area. If you have a spare for that clothing, changing may fix the problem.

This is a good reason that you should not have two of the exact same clothing items: the fabric and seams would annoy your skin in the same way. Backup clothes should be different.

Certain types of clothing may help. For example, on the Pacific Crest Trail in 2003 I had friction rashes on the skin between my thighs. It was very painful; enough that if I hadn't solved the problem, I may not have hiked out of southern California. I often wore tight Lycra® shorts. These shorts did not rub against my legs. Rather, the rubbing occurred between the fabric of the legs of the shorts. That solved my problem.

There are also lubricants that allow the sliding to occur with less damage to the skin, and balms to help heal the skin.

Hair Follicle Infections
Since skin gets dirty and gear and clothing rub on skin, in-grown hairs and pimples may occur. Insect bites may also lead to small infections. It is important that we inspect our skin regularly and treat these to keep them from developing into larger infections.

Once while walking on the Appalachian Trail and once on the Florida Trail I developed a boil or furuncle in my armpit. In both cases, cold rains had been falling non-stop for over a week. Clothes made from technical fabrics are amazing in their ability to keep you warm under such conditions, but people are still not built to remain wet and dirty for days at a time. I imagine the rubbing, the wet skin, and the dirt combined and caused the boils.

Boils are much larger infections of a hair follicle. Puss can collect in a pea to golf ball sized lump. The lump may be red and painful. Hopefully, the puss comes to a white head at the skin surface and can easily be drained. If the conditions that caused the boil persist, the drained puss may cause more boils. It is important to keep the healing area clean and disinfected. Clusters of boils are called carbuncles. Boils may spread infection to the bloodstream, so ending a hike may be a good idea if boils keep forming.

Next: A Few Extra Stories

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