Dermatitis, Contact

BASICS

DESCRIPTION

  • A cutaneous reaction to an external substance in contact with the skin
  • Each type has a different mechanism, whereas the clinical presentation is the same (1).
  • Two main types with distinct mechanism and acuity, but similar presentation (2)
    • Irritant dermatitis (ID): chemical damage to stratum corneum causing inflammatory response; occurs 0 to 48 hours after exposure (3)
    • Allergic contact dermatitis (ACD): occurs after sensitization (first exposure) to a substance; delayed hypersensitivity reaction occurring over hours to days, representing immune cell response (2),(3)
  • System(s) affected: skin/exocrine
  • Synonym(s): dermatitis venenata

EPIDEMIOLOGY

Common

Incidence

Occupational contact dermatitis accounts for up to 70% of occupational skin disease occurrences and affects 20.5/100,000 workers per year in one Australian study. However, it is difficult to quantify due to diverse causes and manifestations; estimated 15% global lifetime incidence (4)

Prevalence

  • Florists, hairdressers, cooks, beauticians, health care workers, and metal-working machine operators have the highest incidence.
  • Predominant sex: male = female
    • Variations due to differences in exposure to offending agents as well as normal cutaneous variations between males and females (eccrine and sebaceous gland function and hair distribution) (5)

Geriatric Considerations
Increased incidence of ID secondary to skin drynessPediatric Considerations
Increased incidence of positive patch testing due to better delayed hypersensitivity reactions (2),(6)

ETIOLOGY AND PATHOPHYSIOLOGY

Hypersensitivity reaction to a substance generating cellular immunity response

  • Plants
    • Urushiol (allergen): poison ivy, poison oak, poison sumac
    • Primary contact: plant (roots/stems/leaves)
    • Secondary contact: clothes/fingernails (not blister fluid—the established eruption is not itself contagious or transmissible)
  • Chemicals
    • Nickel: jewelry, zippers, hooks, and watches (7)
    • Potassium dichromate: tanning agent in leather
    • Paraphenylenediamine: hair dyes, fur dyes, and industrial chemicals
    • Turpentine: cleaning agents, polishes, and waxes
    • Soaps and detergents
  • Topical medicines
    • Neomycin: topical antibiotics
    • Thimerosal (Merthiolate): preservative in topical medications
    • Anesthetics: benzocaine
    • Parabens: preservative in topical medications
    • Formalin: cosmetics, shampoos, and nail enamel

Genetics

Increased frequency of ACD in families with allergies

RISK FACTORS

  • Occupation
  • Hobbies
  • Travel
  • Cosmetics
  • Jewelry

GENERAL PREVENTION

  • Identify and avoid causative agents.
  • Use of protective gloves (with cotton lining) may be helpful.

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