A runny nose, often the result of excess mucus production in the nasal tissues, is a very familiar and often bothersome symptom which is usually caused by the common cold or allergies. Also referred to as rhinorrhea, another source of watery and thin secretions could be temporary factors such as tears, spicy food or cold weather. Less commonly, rhinorrhea may be a symptom of something serious, such as a cerebrospinal fluid drip, or a leak of brain fluid.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Infectious Causes

A runny and watery nose may be caused by anything that irritates the nasal tissues. This symptom is frequently caused by an upper respiratory infection (URI), such as the common cold, and sometimes caused by a sinus infection. If related to a URI, this discharge is a result of the nasal tissues being inflamed by the cold virus, and symptoms of cough, sore throat and fatigue are also common. Sinus infections, caused by a virus, bacteria or mold, have similar symptoms but headache and facial pain may also occur.

Allergens or Irritants

Allergies are another common cause of rhinorrhea. If related to an allergen, or allergy-causing substance, symptoms of sneezing and itching are often present. Allergies cause a release of histamine, a chemical important to the body's immune response. Histamine makes it easier for white blood cells to leak out of tiny blood vessels called capillaries, aiding the body's immune response, but also causing fluid to escape the mucus membrane in the nostrils -- causing a runny nose. Some people have a condition called vasomotor rhinitis, which has overlapping symptoms with allergies but is not considered an allergic reaction 1. In this condition, irritants such as smoke, perfume or even spicy food causes excess mucus production, which can also lead to a runny, watery nose.

Cold Air and Tears

Rhinorrhea is also caused by situations or environmental triggers, rather than a infection-causing virus or bacteria. For instance, breathing cold air into the nostrils can cause liquid from the air to vaporize, and cold air can cause more mucus production in order to moisturize the nasal passages -- both of which can lead to a runny nose. Secretion of tears, or crying, can also cause:

  • a watery
  • runny nose if the tear ducts overflow,
  • excess tears drip down the nasal passage

Serious Causes

Watery discharge coming out of one nostril could signify a cerebrospinal fluid (CSF) leak, or leak of brain fluid -- particularly if this symptom starts after an injury to the head. CSF rhinorrhea occurs when there is a small hole or tear in the membrane surrounding the brain. If untreated, this leak can lead to a serious infection or other complications. Other rare medical conditions or even medication side effects may be the cause of a watery, runny nose, so see a doctor if you have an unexplained and persistent rhinorrhea without obvious cold or allergy symptoms.

Warnings and Precautions

The treatment for the most common causes of rhinorrhea involves patience, understanding and home treatments -- which may include over-the-counter or prescription medications to lessen your symptoms or ward off allergies. It also helps to drink plenty of fluids to keep mucus thin, and to blow your nose to help relieve symptoms. Taking steps to avoid any exposure to allergens or irritants is also important. See your doctor, however, if you need advice on treating allergies or if you think you have a bacterial infection -- characterized by facial pain or swelling, ear pain, fever, yellow or green discharge or symptoms that last longer than 10 days.

Reviewed by: Kay Peck, MPH, RD