A Rugby Football Union disciplinary panel dismissed the charge against Tuilagi on Tuesday night, leaving him free to join the rest of the England squad in flying out for the three-Test series.
And his Leicester team-mate Flood came through his first full training session in almost a month after an ankle injury, almost certainly earning him a place back in Lancaster's plans after missing last weekend's Aviva Premiership final.
Centre Tuilagi had been cited for an alleged tip-tackle on Harlequins' Danny Care early in the final, for which he was only warned by referee Wayne Jones, and which would almost certainly have ruled him out of the tour if he had been found guilty.
But after a two-hour meeting at a hotel in Bristol, the charge against Tuilagi was dropped after a three-man Rugby Football Union disciplinary committee ruled they were "not satisfied" that Tuilagi should be penalised.
An RFU statement said: "A citing charge brought against Manusamoa Tuilagi of Leicester Tigers was dismissed.
"An RFU disciplinary panel of Christopher Quinlan QC (chair), Dan White and Nick Dark was not satisfied on the balance of probabilities that the referee was wrong in not sending the player off for a tackle on Harlequins' Danny Care during the Aviva Premiership final between the teams on May 26.
"Tuilagi is therefore free to continue playing and will fly out to South Africa with the England squad."
Lancaster had feared he would be without the powerful 21-year-old for games against the Springboks in Durban, Johannesburg and Port Elizabeth next month, plus two midweek tour matches.