A Guide To Dry Skin Disorders In The Lower Extremity

M. Joel Morse, DPM

   Occlusive emollients such as petrolatum prevent water loss only by acting as a layer of oil on the surface of the skin to trap water and prevent evaporation. Humectant emollients such as Eucerin (Beiersdorf) penetrate the stratum corneum and draw water from the dermis to retain it in the epidermis. Keratolytics such as lactic acid, salicylic acid and glycolic acid help remove scales. Many times all three are together in one product.

   While topical steroids do not treat dry skin, they do decrease the inflammation of the skin and the “itch” factor. Maximum hydration can occur with 60% propylene glycol in water applied under occlusion.19 When using topical steroids, choose a mid-potency steroid for dorsal skin and a high potency to super high potency steroid on plantar skin. All topical steroids have increased absorption through the incomplete skin barrier.

   When discussing the choice of emollients, a continuum exists between oily ointments and water-based creams and lotions. Ointments are best for the driest of skin conditions and for use at home when patients are not wearing tight clothes or working with others. The application of ointments can cause folliculitis in hairy areas, an unusual issue in the foot and ankle. The frequent use of emollients reduces the need for steroids.20 To avoid or treat xerosis, patients should moisturize their feet right after a bath or shower. They should avoid soaking their feet in hot water for long time periods, using drying soaps on the feet or scrubbing feet dry.

   Anecdotal and limited data suggest that gabapentin, cutaneous field stimulation, serotonin antagonists and ultraviolet B phototherapy may reduce itch in some of these patients.

Combating The Effects Of The Sun

The sun adds to the drying out of the skin just like the cool air of winter and the dry air of a desert. If the skin barrier is compromised, patients can have increased dryness. Snow, sand and water increase the need for sunscreens because they reflect the sun’s rays. A sunscreen product acts like a very thin bulletproof vest, stopping the ultraviolet photons before they can reach the skin and inflict damage. It contains organic sunscreen molecules that absorb UV and inorganic pigments that absorb, scatter and reflect UV. There are sunscreens now that help prevent dry skin by moisturizing as well.21

   The sun’s heat dries out areas of unprotected skin and depletes the skin’s supply of natural lubricating oils. In addition, the sun’s UV radiation can cause burning and long-term changes in the skin’s structure. The sun causes dry skin, sunburn and actinic keratosis. Skin appears as dry, flaky and wrinkled.

Other Considerations With Dry Skin Conditions

Cracked heels. Podiatrists frequently see cracked heels due to poor foot mechanics, prolonged standing, being overweight, poor shoe gear, open backed shoes and the usual cause, flip flops. It is the perfect storm of friction, lack of oil producing glands and inadequate shoegear. In these conditions, the fat pad under the heel expands sideways and increases the pressure on the side. If there is any lack of moisture in the heel, it will crack.

   Accordingly, if you have an overweight patient with diabetes who wears house slippers much of the day, expect her to have cracks in the heels. Cracked heels are more common during the winter months although if you spend extended amounts of time in the sun, it can also dry out your skin to cause cracked heels. Medical conditions including diabetes, obesity, thyroid disease and psoriasis may also cause dry, cracked heels.

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