Common Causes of Sinusitis
Recent upper respiratory infections (such as a head cold)
Allergies
Asthma
Crooked bone and cartilage between the nostrils (otherwise known as a deviated septum)
Environmental factors, such as freezing cold air, poorly ventilated indoor air, cigarette smoke, and car exhaust
Polyps
Small objects inserted in the nose (common in children)
Overuse of decongestant sprays