Skin reaction types in contact dermatitis

Skin reaction types in contact dermatitis

Contact dermatitis may be classified into the following reaction types:

• subjective irritancy
  • idiosyncratic stinging and smarting reactions occur within minutes of contact, usually on the face, in the absence of visible changes
  • cosmetic or sunscreen constituents are common precipitants
    
    
• acute irritant contact dermatitis
  • often caused by
    • a single overwhelming exposure or
    • a few brief exposures to strong irritants or caustic agents
      
      
• chronic (cumulative) irritant contact dermatitis
  • results from repetitive exposure to weaker irritants. These irritants may be either
    • wet - detergents, organic solvents, soaps, weak acids and alkalis
    • dry - low-humidity air, heat, powders, paper, cardboard and dusts
      
      
• allergic contact dermatitis
  • this involves sensitization of the immune system to a specific allergen or allergens with resulting dermatitis or exacerbation of pre-existing dermatitis
    
    
• phototoxic, photoallergic and photoaggravated contact dermatitis
  • some allergens are also photoallergens
    
    
• systemic contact dermatitis (systemic allergic dermatitis)
  • occurs following systemic administration of a chemical, usually a drug, to which topical sensitization has occurred previously
    
    
• protein contact dermatitis
  • repetitive handling of proteins, usually foods, results initially in immediate urticarial symptoms and signs, but later progresses to a dermatitic reaction
  • proteins may be
    • vegetables - potato, garlic
    • meats, fish - in food handlers
    • flour, enzymes - in bakers and pharmaceutical manufacture
    • animal dander and fluids - in veterinarians and abattoir workers

Reference:

1. Johnston GA et al. British Association of Dermatologists' guidelines for the management of contact dermatitis 2017. Br J Dermatol. 2017;176(2):317-329