The handkerchief is a vital bit of stage business in this play. Point out its dramatic function in terms of proving or disproving infidelity and moving the action of the play along.
In Shakespeare's Othello, the handkerchief is an incredibly important symbol. First, Othello tells Desdemona that his mother had given him the handkerchief as a sign of her love for him. As a result, Othello views the handkerchief as a token of his mother's love, which is important because Othello is portrayed as a bit of an outsider in the play. He recognizes that others around him have misgivings because he is a Moor, so the love of his mother strengthens his identity. Next, Othello gives the handkerchief to Desdemona as an act of giving himself to her--Othello wants to show Desdemona that she means the world to him as he meant the world to his mother. In this way, the handkerchief is more than just a symbol of Othello's love, it is a symbol of his soul. Finally, when Desdemona "loses" the handkerchief and Othello sees it on Cassio, he is absolutely enraged and dispossessed because he feels that Desdemona has completely abandoned him and his feelings for her. So, the importance of the handkerchief is developed over the course of the play so that the impact of its being lost and found on Michael Cassio has the utmost impact.