Contact Dermatitis

Basics

DESCRIPTION

An acute or chronic inflammation of the dermis and epidermis as result of either direct irritation to the skin (irritant contact dermatitis) or delayed-type (type IV) hypersensitivity reaction to a contact allergen (allergic contact dermatitis)

EPIDEMIOLOGY

INCIDENCE

Incidence in children is not known.

PREVALENCE

  • Irritant contact dermatitis: Most cases of contact dermatitis (>80%) are due to irritants.
    • Skin reactivity is highest in infants and tends to decrease with age.
  • Allergic contact dermatitis
    • Because children have less time to develop sensitivities, it is less common in infants and children than in adults.
    • Prevalence increases with age.
    • Overall prevalence is ~13–23% and has been increasing in children, perhaps due to more frequent exposure to allergens at a younger age or improved diagnosis.
    • Contact sensitization may complicate the course in >40% of patients with atopic dermatitis.

RISK-FACTORS

  • Irritant contact dermatitis
    • Frequent hand washing or water immersion
    • Atopic dermatitis: Chronically impaired barrier function increases susceptibility to irritants.
    • Genetic factors
    • Environmental factors such as cold/hot temperatures or high/low humidity disrupt the skin barrier.
  • Allergic contact dermatitis
    • Atopic dermatitis
    • Skin barrier disruption from injuries or wounds
    • Genetic factors
    • Increased exposure to allergens

GENERAL-PREVENTION

Minimize contact exposure to known or potential irritants and allergens and maintain the barrier function of the skin.

PATHOPHYSIOLOGY

  • Irritant contact dermatitis does not involve an immune response and thus can occur with the first exposure to the irritant. Multiple mechanisms are involved, including:
    • Direct damage to keratinocytes by chemicals (soaps, detergents) or physical irritants (moisture, friction) with resulting disruption of the epidermal barrier and localized release of proinflammatory cytokines
    • Chronic exposure may stimulate cell proliferation, resulting in acanthosis and hyperkeratosis with postinflammatory hypo- or hyperpigmentation.
  • Allergic contact dermatitis requires initial exposure and sensitization to an allergen and only occurs in susceptible individuals. Repeated exposure leads to the development of a type IV hypersensitivity reaction resulting in proliferation of sensitized T lymphocytes.
    • Strong antigens may require only one exposure, whereas weaker antigens may require multiple.
    • Exposure can occur transepidermally or systemically.
  • Both processes result in nonspecific findings of dermal and epidermal edema and inflammation and may be indistinguishable from other forms of inflammatory dermatitis.

ETIOLOGY

  • Irritant contact dermatitis
    • Frequent hand washing or water immersion
    • Soaps and detergents
    • Saliva (lip licking or thumb sucking)
    • Urine and feces (see “Diaper Rash”)
    • High concentrations of most chemicals can induce irritant contact dermatitis, whereas mild irritants may induce inflammation only in susceptible individuals.
  • Allergic contact dermatitis
    • Nickel and other metals (gold, cobalt)
    • Hair products (ammonium, 5-diamine)
    • Solvents (toluene-2)
    • Cleansers, shampoos (cocamidopropyl betaine)
    • Additives to medications, cosmetics (thimerosal, mercuric chloride)
    • Rubber
    • Fragrances (balsam of Peru [BOP])
    • Dyes (cobalt, potassium dichromate, black henna)
    • Formaldehydes
    • Topical antibiotics (neomycin, bacitracin)
    • Topical corticosteroids
    • Emollient components (lanolin alcohol)
    • Plants (Toxicodendron species; e.g., poison ivy, poison oak, and poison sumac, which contain the allergen urushiol)

ASSOCIATED-CONDITIONS

Atopic dermatitis or other chronic dermatoses

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