Skin, Nails, and Blood Vessels

In many ways, the quality of the skin, nails, and blood vessels in and on the foot is a general reflection of our overall health. These areas, like all others within the foot that are not as noticeable, are greatly influenced by diet and nutrition, stress, the brain, our training, and other lifestyle habits.

The skin is obviously important for normal foot function. It protects the structures inside the foot, is an important site for nerve endings, and cushions the foot with the help of a fat pad under the calcaneal (heel) bone.

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The skin contains many nerve endings for foot-sense, especially on the bottom of the foot. The skin on the feet is very durable, especially on the sole, and can withstand many more pounds of force compared to the hand and fingers before it is cut open. When the skin is subject to chronic stress, such as excessive wear and tear, calluses develop due to a thickening of the skin.

Calluses are almost always caused by shoes that don’t perfectly match the needs of our feet and can be secondary to toe deformities such as a hammertoe or bunion. They typically occur over a bony prominence. A callus that forms on a toe is called a corn. Calluses are usually not painful except certain types that are usually on the bottom of the foot. These may be plantar keratoses, or seed calluses, and are very small. Some calluses put enough pressure on the metatarsal joints to cause pain in the joint. Calluses can usually be differentiated from warts by pinching both sides together—warts are generally tender and calluses are usually not, with the rare exception noted above.

Toenails are adversely affected by trauma, most often by shoes. An ingrown toenail usually occurs in the big toe due to either poor fitting shoes or improper nail trimming, or both. This problem can lead to fungal or bacterial infections.

Another problem found in toenails is the so-called blackened nail. This problem is very common in runners but is found in cyclists and others as well. A blackened toenail is usually due to trauma directly on the nail, which darkens from bruising. The nail may ultimately fall off. A darkened toenail usually means the shoe is too small or otherwise not properly fitting the foot. Some dark toenails are also due to chronic fungal infections.

Blood vessels in the foot are very important to maintain the health of all the structures I’ve discussed. The arteries bring nutrient-rich blood into the foot, in the form of glucose, fat, protein, vitamins, minerals, and others, including oxygen. The veins carry blood back to the heart and remove carbon dioxide, excess water, and waste products from the foot. Poor blood flow can be due to poor muscle function or abnormally narrowed or closed blood vessels, often seen in early disease conditions. This can cause or aggravate existing foot problems from within. Improper blood flow can also cause skin ulceration, common in diabetics.