Compatibility summary
You will need a travel adapter in El Salvador; plug types used there differ from Italy. Voltage differs by more than 20% — a voltage converter may be needed for some appliances.
Plug comparison
Italy plug types: C F L
El Salvador plug types: A B
There is no common plug type between Italy (C F L) and El Salvador (A B). You need a travel adapter.
Voltage comparison
Italy: 230V, 50Hz
El Salvador: 120V, 60Hz
Voltage converter recommended (Italy 230V vs El Salvador 120V).