| Cutaneous anthrax | Painless, necrotic ulcer with a black central eschar; surrounded by characteristic, nonpitting edema |
| Contagious ecthyma | Weeping nodule; scab formation but no distinctive, large eschar; occurs mostly on hands |
| Ecthyma gangrenosum | Lesions usually larger than 3 cm in diameter; highly associated with Pseudomonas aeruginosa infection |
| Fixed drug eruption | Violaceous or dark erythema; recurrence at same location with drug rechallenge; rarely bullous |
| Necrotic arachnidism | Quick necrosis development in 12 to 24 hours; painful |