Sergio Aguero was given a straight red for gobbing at Matt Taylor.
Matchwinner El Hadji Diouf was also left covered in spit after a first-half clash, says The Sun and Bolton boss Gary Megson said: "Clearly, there is no place for that in the game. If there is evidence I would expect UEFA to take action."
Megson added: "El-Hadji has not mentioned anything to me though.
"He is a player who - everyone knows - has been punished in the past and still suffers for it."