What is Post Nasal Drip?
Post nasal drip can be described as either a runny nose or a stuff nose.

Runny nose occurs when nasal tissues and blood vessels produce excess fluid or mucous that runs out of your nose or down the back of your throat. Runny nose can be caused by a cold, influenza, allergies to such things as dust, pollen or pet dander, or as a response to irritants such as tobacco smoke. Other irritants, such as spicy foods, also can trigger a runny nose. Some people have a chronically runny nose for no apparent reason -- a condition called nonallergic rhinitis. Runny nose may or may not be accompanied by nasal congestion.

A runny nose may be annoying and uncomfortable, but it usually clears up on its own. Sometimes a runny nose indicates a more serious problem.

Nasal congestion or stuffy nose occurs when nasal tissues and blood vessels become swollen with excess fluid, causing a stuffy feeling. Nasal congestion can be caused by a cold, influenza, allergies to such things as dust, pollen or pet dander, or as a response to irritants such as tobacco smoke. Some people have a chronically congested nose for no apparent reason -- a condition known as nonallergic rhinitis. Nasal congestion may or may not be accompanied by a nasal discharge or runny nose.

Nasal congestion usually is just an annoyance for older children and adults. But nasal congestion can be serious in infants, who might have a hard time nursing or breathing as a result.

Causes

1)Acute sinusitis
2)Bright lights
3)Bronchiolitis
4)Chickenpox
5)Chronic sinusitis
6)Churg-Strauss syndrome
7)Cluster headache
8)Cold temperature
9)Common cold
10)Decongestant nasal spray overuse
11)Deviated septum
12)DiGeorge syndrome
13)Drug addiction
14)Dry air
15)Dust mite allergy
16)Food allergy
17)Hay fever
18)Hormonal changes
19)Influenza (flu)
20)Latex allergy
21)Lodged object
22)Measles
23)Medications
24)Milk allergy
25)Mold allergy
26)Nasal polyps
27)Nonallergic rhinitis
28)Occupational asthma
29)Peanut allergy
30)Perfume
31)Pet allergy
32)Pregnancy
33)Respiratory syncytial virus (RSV)
34)Roseola
35)Rubella
36)Shellfish allergy
37)Soy allergy
38)Spicy foods
39)Stress
40)Swollen lymph nodes
41)Thyroid problems
42)Tobacco smoke
43)Wegeners granulomatosis
44)Wheat allergy
45)Whooping cough

Adopted from mayoclinic.com