Definition of Runny nose
Runny nose: The production of extra mucus by the nose. Rhinorrhea is the medical term for this common problem. The nose makes extra mucus whenever something that is in the nose, such as pollen or dust, needs to be removed. Mucus formation is also part of the histamine reaction to allergies and of the body's defenses during respiratory infections.
Last Editorial Review: 3/30/2012
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