• The terms eczema and dermatitis are often used interchangeably and describe an inflammatory skin reaction to both endogenous and exogenous agents.
  • Clinical and histologic findings are variable and represent the final common expression for many disorders.
• Commonly identified subsets within this category of skin disorders include:
  • Atopic dermatitis
    • Cutaneous expression of an atopic state, characterized by a family history of asthma, hay fever, and/or dermatitis
  • Contact dermatitis
    • Inflammatory process in skin caused by an exogenous agent that directly or indirectly injures the skin
      • Irritant contact dermatitis: caused by 1 or more inherent characteristics of a compound
      • Allergic contact dermatitis: caused by a specific immune response to the contact antigen
  • Hand eczema
    • Common, chronic form of contact dermatitis; often occupation-related
    • May be associated with atopic dermatitis or may occur alone
  • Dyshidrotic eczema
    • A blistering itchy rash of the hands and feet
  • Nummular eczema
    • Characterized by circular or oval "coin-like" lesions
  • Lichen simplex chronicus
    • May represent the end stage of various pruritic and eczematous disorders
    • Well-circumscribed plaques with lichenified or thickened skin due to chronic scratching or rubbing
  • Asteatotic eczema
    • Mildly inflammatory dermatitis that develops in areas of extremely dry skin, especially during dry winter months
    • Also known as xerotic eczema or winter itch
  • Stasis dermatitis
    • Dermatitis on the lower extremities secondary to venous insufficiency and chronic edema
  • Seborrheic dermatitis
    • Common, chronic skin disorder characterized by greasy scales overlying erythematous patches or plaques

Epidemiology

Atopic dermatitis

• Prevalence
  • Accounts for 10–20% of visits to dermatologists
  • ~20% of infants and young children experience symptoms; 60% continue to have atopic dermatitis in adulthood.
  • > 15 million people in the U.S. are affected.
  • Increasing worldwide
• Sex
  • Affects both men and women
• Age
  • 50% present within first year of life.
  • 80% present by 5 years of age.

Contact dermatitis

• Incidence
  • Occupation-related form affects > 60,000 people annually in the U.S.
  • Accounts for 4–7% of visits to dermatologists
• Race
  • Thought to be more prevalent among white persons
• Sex
  • Female-to-male ratio, 2:1
• Age
  • Most common during adulthood
  • Irritative dermatitis common in infants (e.g., diaper dermatitis)

Hand eczema

• No epidemiologic statistics available

Dyshidrotic eczema

• Prevalence
  • ~5% to 20% of patients with hand eczema
• Geographic distribution and seasonality
  • More common in warmer climates
  • More common in spring and summer months of temperate climates
• Age
  • Affects all ages (mean age, 38 years)
  • Frequency decreases after middle age.

Nummular eczema

• Sex
  • More common among men than women
• Age
  • Most commonly seen in middle-age

Lichen simplex chronicus

• Sex
  • Affects more women than men
• Age
  • Usually presents from 20–50 years of age

Asteatotic eczema

• Seasonality
  • More common in winter months
• Age and sex
  • More common in men > 60 years of age than in women
  • Can also occur in younger patients

Stasis dermatitis

• Age
  • Affects 6–7% of patients > 50 years of age in the U.S.
  • Incidence increases with age.
• Sex
  • Slightly more common in women than in men

Seborrheic dermatitis

• Prevalence
  • 3–5% worldwide
  • Dandruff occurs in 15–20% of the population.
• Sex
  • Slightly more common in men than in women
• Age
  • Peaks at 40 years of age; less severe in older people
  • May occur within first few weeks after birth ("cradle cap"); rare in children beyond infancy

Risk Factors

• Atopic dermatitis
  • Genetic predisposition
    • If both parents are affected, 80% of children develop the disorder.
    • If 1 parent is affected, slightly more than 50% of children develop the disorder.
    • Personal or family history of atopy (asthma, allergic rhinitis, food allergies, or eczema)
  • Risk factors for atopic dermatitis during the first 2 years of life [1]
    • Shortening of the duration of exclusive breast-feeding
    • Male sex
    • Parental history of atopic dermatitis, asthma, or hay fever
    • Increased maternal age
    • > 37 weeks gestation
    • Increased head circumference
    • Increased birth weight

• Contact dermatitis
  • Irritant form
    • Exposure to an irritating exogenous compound, such as a concentrated acid or base
  • Allergic form
    • Exposure to plants that contain the sensitizing antigen urushiol, an oleoresin containing the active ingredient pentadecylcatechol (especially members of the family Anacardiaceae, including the genus Toxicodendron [poison ivy, poison oak, poison sumac])
    • Exposure to skin, clothing, tools, pets, and other items that have contacted oleoresin, which may be active even after months of storage
    • Exposure to other antigens that may be more difficult to identify, especially if exposure is chronic and skin becomes thickened and scaly
• Hand eczema or dyshidrotic eczema
  
  • Chronic, excessive exposure to water and detergents or other irritants
  • Exposure to rubber or latex gloves
  • Occupation that exposes hands to chronic insult
• Nummular eczema
  • Risk factors unknown
• Lichen simplex chronicus
  • Tendency to develop eczema or contact dermatitis
• Asteatotic eczema
  • Dry skin
  • Drying, often cold, environmental conditions
• Stasis dermatitis
  • Edema
  • Poor circulation, particularly associated with aging
• Seborrheic dermatitis
  • Risk factors unknown

Etiology

• Atopic dermatitis
  • Underlying causes are only partially defined.
  • Immunoregulatory abnormalities have been identified.
    • Increased IgE synthesis
    • Increased serum IgE specific to foods, aeroallergens, bacteria, or bacterial products
    • Increased expression of CD23 (low-affinity IgE receptor) on monocytes and B cells
    • Impaired delayed-type hypersensitivity reactions
  • Insufficient evidence to define it as a classical autoimmune disease [2]
    • Autoantigens have been identified.
    • Studies suggest that this disease is initiated, maintained, and perpetuated by the actions of cytokines, chemokines, T cells, antigen-presenting cells, and other inflammatory cells.
    • Studies suggest that this disease involves skin barrier defect and angiogenesis.
      • Mutations of the epidermal barrier protein filaggrin (encoded by FLG)
      • 70% of individuals homozygous or compound heterozygous for FLG null alleles develop atopic dermatitis.
• Contact dermatitis
  • Irritant form
    • Irritant produces a direct local cytotoxic effect on the cells of the epidermis, with a subsequent inflammatory response in the dermis.
    • Most common irritants are wet work, soaps, and detergents.
  • Allergic form
    • Delayed-type hypersensitivity mediated by memory T lymphocytes in the skin
    • Most common cause: exposure to chemicals in certain plants
      • Poison ivy
      • Poison oak
      • Poison sumac
    • Other chemical causes
      • Nickel sulfate
      • Potassium dichromate
      • Thimerosal
      • Neomycin sulfate
      • Fragrances
      • Formaldehyde
      • Rubber-curing agents
• Hand eczema (form of contact dermatitis)
  • Delayed-type hypersensitivity reaction, often to agents used to cross-link rubber in rubber gloves
  • Immediate-type hypersensitivity reaction, including possible anaphylactic reaction, to latex
  • Chronic, excessive exposure to water and detergents may initiate or aggravate this disorder.
• Nummular eczema
  • Unknown
• Lichen simplex chronicus
  • Chronic scratching or rubbing of pruritic or eczematous skin
• Asteatotic eczema
  • Extremely dry skin being exposed in dry winter months
• Stasis dermatitis
  • Venous insufficiency and chronic edema of the lower extremities
• Seborrheic dermatitis
  • Unknown

Associated Conditions

• Atopic dermatitis
  • Allergic rhinitis or asthma is present in 80% of patients.
• Hand eczema
  • Other cutaneous disorders, such as atopic dermatitis
• Chronic stasis dermatitis
  • Dermal fibrosis (brawny edema)
• Seborrheic dermatitis
  • Parkinson’s disease
  • Cerebrovascular accident
  • HIV infection