Munchkins: Apocolypse Preparing for the 7th seal
OK, I looked up the rules. On page 5 is a section called 'WHEN TO PLAY CARDS'. In it you find:


  Items – Playing Them
  
  Any Item card may be played to the table as soon as you get it, or at
  any time on your own turn other than in combat (unless the card itself
  says otherwise).


So, if you have no combat and it is your own turn, you can play item cards.