Some says eczema flare will have rotten or fishy smell. It would be always unpleasant. It worsens with sweats.
It could be due to the secondary infection of the skin. The odor is due to the tissue breakdown by bacteria.
Most often the wound is oozing or weeping. It looks slimy. It should not have any smell if it’s dry.
Crusty lesions can cause the above too, especially if you have cradle cap or seborrheic dermatitis.
In this case, you should discuss with your doctor. He would prescribe you oral antibiotic or topical antibiotic if the lesions are pustular and localized.