3 learning resources available for this topic
Contact dermatitis is an inflammatory skin reaction caused by direct contact with irritants or allergens, resulting in localized redness, swelling, and often vesicle formation. It represents one of the most common occupational and environmental skin disorders, affecting millions of people worldwide through exposure to substances like metals, chemicals, plants, or cosmetics.
Irritant contact dermatitis occurs through direct cytotoxic damage to keratinocytes from substances that breach the skin barrier, triggering immediate inflammatory cascades. Allergic contact dermatitis involves a delayed-type hypersensitivity reaction (Type IV) where sensitized T-cells recognize hapten-protein complexes, leading to inflammatory mediator release and characteristic delayed onset symptoms 24-72 hours after exposure.
Diagnosis relies on detailed exposure history, characteristic distribution patterns that correspond to contact areas, and patch testing to identify specific allergens in suspected allergic cases. The temporal relationship between exposure and symptom onset helps differentiate irritant (immediate to hours) from allergic contact dermatitis (1-3 days), while the clinical presentation and response to avoidance measures guide treatment decisions and prevention strategies.