Xerosis

Xerosis, or dry skin, is caused by a relative loss of water from the skin through evaporation and a lack of normal desquamation and lubrication.
Xerosis is especially prevalent in persons who are older than 65 years of age who tend to have a decrease in the production of sebum, the skin's natural lubricant and sealant.
As skin loses moisture its surface tends to fissure.
Xerosis tends to be most apparent on the hands and lower legs.
Dry areas may result in dermatitis, crazy-paving appearance on the lower legs or round patches scattered over the trunk and limbs (a dry form of nummular eczema). Sometimes the dry skin is just itchy, without much of a rash (“winter itch”).
Contributing factors include hypothyroidism, cool weather, especially when windy or the humidity is low, excessive bathing, showering or swimming, especially in strongly chlorinated, hot or cold water, excessive contact with soap, detergents, and solvents.

Asteatotic Eczema

Asteatotic eczema occurs almost exclusively in adults.
This form of eczema is a common, sometimes pruritic, low-grade dermatitis that presents with seasonal recurrences in the winter.
Early on, the affected skin feels and looks dry; later, an inflammatory dermatitis may evolve.
Lesions most commonly appear on the shins, arms, hands, and trunk (see Chapter 13: Eczema and Related Disorders).
The eruption often resembles the surface of a cracked porcelain vase and is often referred to as erythema craquelé. It is also likened to the appearance of a dry riverbed (Fig. 25.1).
A clinical variant consists of small, square-shaped, rectangular, or annular, scaly plaques that are often mistaken for tinea corporis (ringworm) and are often treated as such (Fig. 25.2).

Atopic Dermatitis

Dry, xerotic, exquisitely sensitive, itchy skin is a major feature of atopic dermatitis (see Chapters 4 and 13 for management of this condition).
Atopic skin is characterized by decreased water content, increased water loss, and reduced water-binding capacity, as well as epidermal hyperproliferation, resulting in lichenification (an exaggeration of normal skin markings) and buildup of scale. Underlying causes include intrinsic defects in the epidermal barrier, alterations in the cutaneous innate, and adaptive immunity, as well as environmental triggers.
Patients usually have a personal or family history of allergies, asthma, or hay fever.
In both young and old, “chapped lips” is a very common problem, especially in individuals who have atopic cheilitis or an atopic predisposition (Fig. 25.3).
In addition to scaly eczematous plaques, such patients may develop painful linear cracks or fissures from xerosis, particularly on the palms, soles, and fingertips (Figs. 25.4 and 25.5).

Differential Diagnosis

Ichthyosis Vulgaris (see Discussion in Chapter 4: Eczema in Infants and Children)

Ichthyosis vulgaris (the most common variant of ichthyosis) resembles dry skin; however, it is actually caused by over adherence of scale.
Frequently associated with atopy.
Skin with ichthyosis vulgaris resembles fine fish scales and tends to be most clinically obvious on the shins.

Dry Skin that is not “Dry” (Exfoliation)

Many patients complain of “dry skin” from the use of topical retinoids such as Retin-A for the treatment of acne. Actually, the “dryness” is scaling that results from the exfoliative effect of the topical retinoid.
Another common complaint is that of scaling and “dryness” from seborrheic dermatitis of the face and scalp. In such cases, the skin is not always dry and deprived of moisture; rather, the scales and flakes may derive from the inflammatory process.

Management

Moisturizers

Moisturizers do not add water to the skin, but they help retain or “lock in” water that is absorbed while bathing. Therefore, moisturizers should be applied while the skin is still damp.

Other Strategies

For the dermatitis, itching, and erythema of atopic dermatitis or asteatotic eczema, low- to medium-potency (class 4 to 6) topical corticosteroids are valuable. In severe cases, more potent topical corticosteroids (class 1 to 3) may be applied for brief periods when necessary.
Tepid showers and baths that are less frequent and shorter may be helpful.
Soap avoidance (on affected areas), mild soaps (e.g., Dove, Basis) or a soap substitute (e.g., Cetaphil non-soap gentle cleanser) may be tried. However, excessive use of any soap or substitute should be avoided, especially on affected areas. CeraVe cream or Eucerin Daily repair cream are also excellent options.
Adhesive dressings (Band-Aids) are effective in promoting healing of fissures.
Lined gloves, worn while washing dishes, can keep hands dry.
Scarves, gloves, and other apparel can help to provide adequate protection from exposure to outdoor cold.
The use of room humidifiers and the ingestion of copious amounts of water are of questionable value.

SEE PATIENT HANDOUT “Dry Skin (Xerosis)” IN THE COMPANION eBOOK EDITION.

Outline
Asteatotic Eczema
Atopic Dermatitis