Italics are not working

Italics are not working in forum messages. They work when we are writing the message, but when it gets posted there is no italicized text. Then if I edit the message, the italics work but then again if I apply the update the italicized text is not shown using italics. So I looked at the HTML and there is a class or style (I forget what) that if I remove it (the class or style) then italics work. So the fix is probably very easy but the problem has existed for at least a week.