Contact Dermatitis

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

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)

Commonly Associated Conditions

Atopic dermatitis or other chronic dermatoses