Both were forced off during Saturday's 1-0 win at Crystal Palace.
On Alisson, he began: "The latest is that we don't know but what we do know is that if a player walks off like he did, that normally means that he is not in the Brazil squad and I don't expect him to be in the team in the first game we play after (the international break).
"We have to wait and see, but it is going to take a few weeks I assume for him to be back. I think it is (his hamstring)."
On Mac Allister, the head coach added: "He went off because of an injury, but how bad it is is difficult for me to judge in this moment.
"He could have continued playing, like you saw, because it didn't happen one second before half-time, but he felt it a bit too much and he said he didn't think it was good to keep on playing because you never know if you will make it worse.
"Now, what is the exact situation, can he go to Argentina? Can he play over there? That is difficult for me to tell you now.
"(It's an issue) in his groin area."