The hands are one of the most expressive parts of the body, providing the structures needed to write, draw, paint, dance, and express affection. It is frequently said that much can be said about people from their handshake, which is an assessment of the skin, muscle, and bone that form the hand. The hand can express gender, occupation, and age. Female hands are small while male hands are large and muscular. People who work with their hands outdoors have a much different skin feel than persons who type on a computer for much of the day. Children have soft, doughy, padded hands while the elderly have thin, sinewy, bony, arthritic hands. Hands are what make humans unique from every other living thing on the earth.
Anatomy and Physiology
The hands are formed of many tiny muscles and bones that account for their agility. They are that part of the body that most frequently touches the outside world and can serve as a vector, bringing infection to the vulnerable nose, eye, and mouth tissues. The hands also sustain considerable chemical and physical trauma. They are washed more than any other body area, yet are completely devoid of oil glands on the palmar surface.
While the stratum corneum of the palm is uniquely designed to withstand physical trauma, it is not designed to function optimally when wet. Water destroys the resistive physical strength of the palmar skin, which is why hand blisters are more common when the hand is perspiring heavily. The palmar surface of the hand has numerous sweat glands, known as eccrine glands, which are largely under emotional control. Palm sweating may occur in warm weather, but may also occur under stressful conditions.
The hand responds to trauma by forming thickened skin, known as a callus. Calluses are formed from retained layers of keratin that form a dead skin pad over the area subjected to repeated physical trauma. For example, the palm of the hand will callus to protect the small bones in persons who use a hammer. The finger will callus in the location where a pencil is held in both children and adults. While the body forms a callus to protect underlying tender tissues, the callus can also cause dermatologic problems. Since a callus is made of retained keratin, it is dehydrated and inflexible and will fissure readily with trauma. Once the keratin is fissured, it cannot be repaired, since the callus is nonliving. This leads to a discussion of the most common dermatologic disease considerations involving the hand.
Common Dermatologic Disease Considerations
Dermatologic disease needs to be divided into those conditions that affect the dorsum or back of the hand and those that affect the palm of the hand. This is an important distinction because the two skin surfaces are quite different. The dorsum of the hand is thinner skin that becomes increasingly thinner with age. After the face, the back of the hand is generally the most photoaged skin location. The skin of the hand loses its dermal strength early leading to decreased skin elasticity, which can be simply measured by pinching the skin on the back of the hand and watching for the amount of time it takes for the skin to
rebound to its original conformation. This easy to perform test is an excellent measure of the hand skin age. Skin that takes a long time to return to normal configuration is more photoaged than youthful skin that bounces back energetically. In addition to losing elasticity, photoaged skin also becomes irregularly pigmented leading to dark areas, known as lentigenes, and light areas, known as idiopathic guttate hypomelanosis. This irregular pigmentation is also accompanied by skin that is easily injured. Injury may be seen in the form of red bruises, affectionately named senile purpura, and tissue tears from minimal trauma, which heal with unattractive white scars.
The palm of the hand is affected uniquely by inflammatory conditions like eczema and palmar psoriasis. Because the palm is the surface that the body uses to pick and touch, it more commonly is affected by chemical and physical trauma. This trauma may manifest as hand eczema, which is usually treated with high potency corticosteroids. In addition, highly occlusive and emollient hand creams are necessary to rehydrate damaged keratin and create an optimal environment for barrier repair. Hand creams are also important in the treatment of psoriasis where too much poor quality skin is produced too quickly. Both of these conditions require carefully selected cleansers and moisturizers, in addition to prescription therapy.
Lastly, the palms can be affected by excessive sweating, a condition medically known as hyperhidrosis. Palmar hyperhidrosis can be physically disabling to persons such that they cannot hold a pen to write or emotionally disabling such that they are uncomfortable shaking hands. As mentioned previously, the eccrine sweat glands on the palms are under temperature and emotional control. Palmar hyperhidrosis is usually more of an emotional condition, since the sweat released by the hands does little to cool the body. The treatment of hyperhidrosis is addressed in Chapter 8.
Hygiene Needs
The hands receive more cleansing than any other part of the body. The basic ritual of “wash your hands before you eat” is an effective method of preventing disease transmission, but may take its toll on the physiologically sebum-lacking skin of the palms. Excessive hand washing can even be considered a medical disease, especially in persons with obsessive-compulsive disorder. There are a variety of methods of washing the hands. Basic hand washing is usually performed with a bar or liquid soap followed by water rinsing. Regimented timed hand washing routines are used to thoroughly remove all bacteria from the hands prior to surgery. Lastly, a variety of hand cleansing antibacterial gels have been introduced, usually based on triclosan, that can be used without water to clean the hands. In general, it is felt that the physical rubbing of the hands to lather the cleanser followed by rubbing in a running stream of water to rinse away the cleanser is important. Both the physical rubbing of the hands and the chemical interaction of the cleanser and water are necessary for optimal hand hygiene.
Skin Care Needs
The skin care needs of the hands go beyond basic cleansing to moisturization, healing, photoprotection, and skin lightening. As mentioned previously, hand moisturization is very important due to frequent cleansing. Hand moisturizers should be designed to occlude the skin reducing transepidermal water loss, rehydrate the skin through the use of humectants, alleviate itch and pain, and smooth the skin surface with emollients. Hand moisturizers with this type of construction can be used for simple dry skin, as well as providing healing qualities for the dermatologic conditions previously discussed.
In addition to moisturization, the hands also need photoprotection both during sports and while driving a car, since photoaging UVA radiation passes through the windshield of a car. Sun protection is a unique challenge for the hands because they are frequently aggressively washed, removing the sunscreen. However, the need for sun protection is obvious when one considers the thin dyspigmented skin that characterizes mature hands. This means that the hands require aggressive anti-aging therapy, discussed in Chapter 11, and skin lightening, discussed in Chapters 13, 14.