Most cases of nasal obstruction are caused by allergies, sinusitis, medication, overuse of nasal sprays and other relatively unhazardous causes. But nasal obstruction can also be caused by a foreign object or anatomical factors, in which case the obstruction may require surgery.

Here are some of the anatomical factors that can cause nasal obstruction:
1. One anatomical cause of some nasal obstructions is a deviated (distorted) septum, which is the partition made of cartilage that separates the two nostrils. A deviated septum may exist at birth or may be caused by a sports injury or other trauma.
2. Some cases of nasal obstruction result from enlarged nasal turbinates. The turbinates are three structures comprised of soft tissue and bone that line the sides of the nasal cavity. If they swell and enlarge they can block the nostrils.
3. Nasal obstruction can also be caused by a type of inflammatory tissue called nasal polyps. These polyps can often grow in the sinuses and nasal cavity. Nasal polyps often affect people with allergies or asthma. The most common symptoms is nasal obstruction.
4. Another cause of nasal obstruction is a collapse of the nasal valve(s). This typically occurs due to narrowness or weakness of the nasal valve. Causes include trauma to the nose or even a prior rhinoplasty procedure that may not have gone well.
5. Nasal obstruction can cause breathing problems and sinus disease, so it must be treated.