Irritant contact dermatitis | Allergic contact dermatitis | |
Etiology | Irritant substances | Allergens |
Mechanisms | Nonimmunologic | Delayed-type hypersensitivity Antigen-specific T cells |
Sites | Localized to the contact areas | At the site of the contact May be widespread |
Symptoms | Burning, stinging, and pain Pruritus may be present | Pruritus |
Onset | May appear after first contact Usually minutes to hours (strong irritant) or 24 hours to 1 week (weak irritant) | Sensitization phase before onset Usually 24 to 72 hours after exposure |
Decrescendo phenomenon | Yes | No |
Clinical manifestation | ||
Acute stage | Erythema, edema, vesicles, and bullae Necrosis and ulceration in severe cases | Erythema, edema, vesicles |
Chronic stage | Fissuring, hyperkeratosis, and scaling | Fissuring, hyperkeratosis, and scaling |
Histopathology | Mild spongiosis, necrosis of epidermal keratinocyte | Spongiosis |
Patch testing | Negative | Positive |