Facebook Unity SDK login permission request pop up for authorized user

I've followed through the InteractiveConsole and FriendsSmash example in Unity and learnt how to request permissions during login and get the friend list of the user.

But there's one little problem bothering me a lot. When FB.Login("email,user_birthday", LoginCallback) is called for an authorized user. The user will be redirected to the Facebook page saying "You have already authorized App-Name".

I'm thinking to only call FB.Login("",LoginCallback) to every user, and then use the FB.API to check if the correct permissions exist, and after that call the original FB.Login method. However, this doesn't seem a very wise way to do this to me.

I did a bit of research but still can't seem to find a nice way to solve this. Can anyone please help me out on this?

Thanks.