Rhinorrhea or rhinorrhoea is a condition where the nasal cavity is filled with a significant amount of mucus fluid. The condition, commonly known as a runny nose, occurs relatively frequently. Rhinorrhea is a common symptom of allergies (hay fever) or certain viral infections, such as the common cold. It can be a side effect of crying, exposure to cold temperatures, cocaine abuse, or withdrawal, such as from opioids like methadone. Treatment for rhinorrhea is not usually necessary, but there are several medical treatments and preventive techniques available.
The term was coined in 1866 and is a combination of the Greek terms rhino- ("of the nose") and -rhoia ("discharge" or "flow").
Rhinorrhea is characterized by an excess amount of mucus produced by the mucous membranes that line the nasal cavities. The membranes create mucus faster than they can be processed, causing a backup of mucus in the nasal cavities. As the cavity fills up, it blocks off the air passageway, causing difficulty breathing through the nose.
Air caught in nasal cavities, namely the sinus cavities, cannot be released and the resulting pressure may cause a headache or facial pain. If the sinus passage remains blocked, there is a chance that sinusitis may result. If the mucus backs up through the Eustachian tube, it may result in ear pain or an ear infection. Excess mucus accumulating in the throat or back of the nose may cause a post-nasal drip, resulting in a sore throat or coughing. Additional symptoms include sneezing, nosebleeds, and nasal discharge.