The voice box (larynx) is located at the top of the airway to the lungs (windpipe, trachea) and contains the vocal cords. When they become inflamed or infected, they swell. This can cause hoarseness, and may occasionally cause obstruction of the airway.

The most common form of laryngitis is an infectious illness usually caused by a virus which results in hoarseness. It may also be part of a bacterial infection or part of a common cold, bronchitis, flu, or pneumonia.

Laryngitis often follows or occurs during an upper respiratory infection and is a self-limiting condition. Common laryngitis is not normally associated with any breathing difficulty (respiratory distress).

Several forms of laryngitis occur in children and can lead to significant or fatal respiratory obstruction. These are croup and epiglottitis (discussed under their respective headings).

Other causes of laryngitis include laryngeal polyps, laryngeal paralysis (such as Horner syndrome), premalignant changes of the vocal mucosa, malignant tumors, allergies, and trauma.