When you're face to face with someone who's upset, besides providing comforting words, the best thing you can do is hug them.  The pressure of your warm body on theirs releases a hormone called oxytocin, which is associated with reduced stress levels, growth, healing, and social bonding. In essence, touch in general reduces stress and anxiety.  When a person is touched by a loved one, centers of the brain associated with fear and danger become less active.