The terms eczema and dermatitis are used interchangeably, denoting a polymorphic inflammatory reaction pattern involving the epidermis and dermis. There are many etiologies and a wide range of clinical findings. Acute eczema/dermatitis is characterized by pruritus, erythema, and vesiculation; chronic eczema/dermatitis, by pruritus, xerosis, lichenification, hyperkeratosis, ± fissuring.
ICD-9 : 692-9 • ICD-10 : L25
Contact dermatitis is a generic term applied to acute or chronic inflammatory reactions to substances that come in contact with the skin. Irritant contact dermatitis (ICD) is caused by a chemical irritant; allergic contact dermatitis (ACD) by an antigen (allergen) that elicits a type IV (cell-mediated or delayed) hypersensitivity reaction.
The acute form of ICD occurs after a single exposure to the offending agent that is toxic to the skin (e.g., croton oil, phenols, kerosene, organic solvents, sodium and potassium hydroxide, lime acids) and in severe cases may lead to necrosis. It is dependent on concentration of the offending agent and occurs in everyone, depending on the penetrability and thickness of the stratum corneum. There is a threshold concentration for these substances above which they cause acute dermatitis and below which they do not. This sets acute ICD apart from acute ACD, which is dependent on sensitization and thus occurs only in sensitized individuals. Depending on the degree of sensitization, minute amounts of the offending agents may elicit a reaction. Since ICD is a toxic phenomenon, it is confined to the area of exposure and is therefore always sharply marginated and never spreads. ACD is an immunologic reaction that tends to involve the surrounding skin (spreading phenomenon) and may even spread beyond affected sites. Generalization may occur.
Acute irritant contact dermatitis following the application of a cream containing nonylvanillanid and nicotinic acid-butoxyethylester that had been prescribed for lower back pain. The streaky pattern indicates an “outside job,” the eruption is characterized by massive erythema with vesiculation and blister formation and is confined to the sites exposed to the toxic agent.
Acute irritant contact dermatitis on the hand due to an industrial solvent. There is massive blistering on the palm.
Acute irritant contact dermatitis in resolution. This is a florist who had contact with croton, poinsettias, and butter cup so that it could not be determined which of these was the eliciting plant. Note the streaky pattern of the eruption on the left hand.
Early chronic irritant contact dermatitis in a housewife. This has resulted from repeated exposure to soaps and detergents. Note glistening finger tips (pulpitis).