Description

• A cutaneous reaction to an external substance
• Primary irritant dermatitis is due to direct injury of the skin. It affects individuals exposed to specific irritants and generally produces discomfort immediately after exposure (1).
• Allergic contact dermatitis (ACD) affects only individuals previously sensitized to the substance. It represents a delayed hypersensitivity reaction, requiring several hours for the cascade of cellular immunity to be completed to manifest itself.
• System(s) affected: Skin/Exocrine
• Synonym(s): Dermatitis venenata

Epidemiology

Common

Incidence
Occupational contact dermatitis: 20.5/100,000 workers

• Contact dermatitis represents >90% of all occupational skin disorders.
• 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)

Geriatric Considerations
Increased incidence of irritant dermatitis secondary to skin dryness

Pediatric Considerations
Increased incidence of positive patch testing due to better delayed hypersensitivity reactions

Risk Factors

• Occupation
• Hobbies
• Travel
• Cosmetics
• Jewelry

Genetics
Increased frequency of ACD in families with allergies

General Prevention

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

Pathophysiology

Hypersensitivity reaction to a substance generating cellular immunity response (2).

Etiology

• Plants:
  • Urushiol (allergen): Poison ivy, poison oak, poison sumac
  • Primary contact: Plant (roots/stems/leaves)
  • Secondary contact: Clothes/Fingernails (not blister fluid)
• Chemicals:
  • Nickel: Jewelry, zippers, hooks, and watches
  • Potassium dichromate: Tanning agent in leather
  • Paraphenylenediamine: Hair dyes, fur dyes, and industrial chemicals (3)
  • 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