I think that one point that has to be made on Othello's jealousy is in its uncontrollable nature. Once Iago plants his "medicine" in Othello's mind, it grows and cannot be stopped. Like weeds in a garden, this jealousy dominates Othello. He cannot control it and it cannot be stopped. It spreads everywhere and contaminates everything. Jealousy is shown as a limitless monster, rooted in the individual. It is shown to be impossible to control.
Another point to be made on Othello's jealousy is that it prevents any open and full discussion. I tend to think that the entire tragedy could be resolved if Othello is able to sit and reasonably talk about his fears and insecurities with Desdemona and Cassio. If he is able to simply talk openly about his fears and his insecurities, he could receive validation that would help him. His jealousy is shown to take such a control over him that he cannot speak openly about it, allowing it to fester even more.
Finally, I think that Othello's jealousy is rooted in a personal sense of insufficiency and insecurity. Othello suffers from an insecurity that is personal in nature. To a great extent, he does not believe himself as being worthy of such great endeavors and a wife like Desdemona. He might believe this because he has internalized how society feels about a man of color and an outsider like himself. This sense of insecurity and doubt enables his jealousy to take hold over him. It is this lack of self worth that allows jealousy to assume such a control over his life and drive his downfall.