| Prevalence |
Very common |
Less frequent |
| Symptoms |
Burning, pruritus, pain |
Pruritus |
| Clinical aspects |
Erythema, swelling, blisters and pustules, desquamation, no distant spread |
Erythema, edema, vesicles, bullae, distant spread |
| Sites |
Site of direct contact |
Site of contact and secondary lesions |
| Cause |
Chemical irritants, dose-related response |
Poison ivy, nickel, fragrances, neomycin, metals (jewelry), cosmetics, drugs |
| Prior exposure |
Not necessary |
Essential (lesions appear after re-exposure) |
| Susceptibility |
Everyone |
Susceptible persons |
| Onset |
Rapid onset (4–12 h after contact) |
Delayed onset (more than 24 h after exposure) |
| Mechanism |
Direct cytotoxic effects (non-immune-modulated irritation) |
Type IV T-cell mediated, delayed reaction, patch-test positive |
| Treatment |
Avoidance of the substance |
Antihistamines, topical steroids/oral desensitization |
