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
  • Genetic factors
  • Increased exposure to allergens

General Prevention

Minimize contact exposure to known or potential irritants and allergens.

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 the following:
  • Disruption of the epidermal barrier by chemicals (soaps, detergents) or physical irritants (moisture, friction)
  • Damage to cell membranes and cytotoxic effect on skin cells
  • Chronic exposure may stimulate cell proliferation, resulting in acanthosis and hyperkeratosis. Postinflammatory hypo- or hyperpigmentation may result.
• 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.
• 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)
  • Additives to medications, cosmetics (thimerosal, mercuric chloride)
  • Rubber
  • Fragrances (Balsam of Peru)
  • Clothing dyes
  • Formaldehydes
  • Topical antibiotics (neomycin, bacitracin)
  • Plants (Toxicodendron species; e.g., poison ivy, poison oak, and poison sumac, which contain the allergen urushiol)