Post nasal drip is a common condition that happens when mucus from the back of your nose thickens and drips down into your throat. When this occurs, it can make you cough and try to clear your throat. This can sometimes be accompanied by bad breath and sinus pressure. The symptoms often worsen when you're lying down.

If you're experiencing post nasal drip symptoms, you'll need to identify the cause in order to determine the best course of treatment. There are possible culprits to consider.

Possible Post Nasal Drip Causes

Allergies. People who have allergies often produce more mucus.  To prevent the problem, allergy-proof your home and minimize your exposure to triggers. You may also need an antihistamine to head off the reaction, or a decongestant to control existing symptoms. A nasal spray containing steroids to prevent swelling in your nasal cavities can also be beneficial. Just check with a doctor or pharmacist first to find out what medications will be best for your situation and that are safe to take together.

Cold or flu. Illnesses can produce thicker mucus in larger quantities. Counteract this problem by trying to thin your secretions. Drinking lots of water, avoiding caffeine (which can make the problem worse) and taking a cold or cough medication can help to accomplish this goal. You can also try a saline nasal spray or use nasal irrigation to clean out your nasal passages.

Medications. If you take birth control pills or blood pressure control medications, these may affect your mucus production and post nasal drip can be a side effect. Talk to your doctor about trying a different form of the medication to see if this will help relieve the problem.

Food allergies. If you have a food allergy, your body could respond to any exposure by increasing mucus production. In such a case, you'll want to avoid the offending food and take an antihistamine if you do come into contact with it. If you're at risk for a serious reaction, you'll also need to carry an epi-pen.

An infection. When you have a sinus infection, your mucus will thicken and take on a brighter green or yellow tint. (In most other causes, the mucus should be clear or white.) When an infection occurs, if it's bacterial in nature you'll need antibiotics. Sometimes your doctor will also recommend taking a decongestant or cough medicine along with them. Once the infection clears up, so should the post nasal drip.

Stress as a Cause

If you still feel post nasal drip symptoms, nerves or stress could be to blame. The sensation you feel when you try and clear your throat can be very similar to post nasal drip (although there isn't any drip involved). If your throat muscles tighten and feel like you have a lump in your throat, your body could simply be tense. In that case, try some relaxation exercises to see if that makes a difference.

Sources:

American Academy of Family Physicians (AFP)

http://www.aafp.org/afp/990700ap/family.html
http://www.aafp.org/afp/2004/0515/p2441.html

American Academy of Otolaryngology - Head and Neck Surgery

http://www.entnet.org/HealthInformation/postNasalDrip.cfm