Consider your stomach. What you think is excessive postnasal drip could actually be esophageal reflux, more commonly known as heartburn. Some of the new antihypertensive medications can cause people to have symptoms of postnasal drip when they actually have heartburn. Consider your estrogen level. The hormone estrogen affects the mucous lining of the nasal cavity.
Some oral contraceptives are high in estrogen.
Increasing the amount of estrogen circulating in the body can cause the nasal lining to get more puffy and produce excess mucus. If you have a postnasal drip problem and take the Pill, discuss this with your gynecologist. He may be able to give you a low-dose prescription. Skip the antihistamines. They don't work that well, and they do make you drowsy.