If you have $1-$5 a pair "common" dice, absolutely try it! If you have Hard Rock or Palms LE dice that are seldom seen, and bring much higher prices, that's where I'd use some caution.

If your dice DO happen to have a bad reaction to the foam, you won't see it until you take 'em out of the foam...where contact was made the dice will show the texture of the foam. So, as long as you leave 'em in the foam, they'll look fine.