Watford midfielder Imran Louza faces a six-game ban after being charged with spitting at an opponent in the Hornets' 2-1 defeat by Swansea last Wednesday.
The FA has not named the alleged victim but Louza has until Thursday to respond to the charge.
The Moroccan midfielder signed a contract extension at the Hertfordshire club at the end of September.
Ismaila Sarr gave the home side the lead in the first half of last week's fixture before Olivier Ntcham equalised in the 52nd minute.
Ben Cabango's 98th-minute header then completed a dramatic turnaround victory for Swansea.