Why do people flare their nostrils?

Flaring the nostrils is a common human behavior that serves several purposes:

1. Increased Air Intake: When a person flares their nostrils, it widens the nasal passages, allowing for a greater volume of air to be inhaled. This is particularly useful during periods of increased respiratory demand, such as during exercise, heavy breathing, or in situations of increased oxygen requirement.

2. Scent Detection: Flaring the nostrils can help enhance the sense of smell by increasing the surface area of the nasal mucosa exposed to scents. It improves the detection and identification of odors by allowing more odor molecules to reach the olfactory receptors.

3. Facial Expression: Nostril flaring can also be a form of facial expression. It is often associated with anger, fear, or surprise. In these emotional contexts, flaring the nostrils may serve as a way to convey or emphasize certain feelings.

4. Communication: In some cultures, nostril flaring can have specific social meanings. For example, in certain tribes, it might be a sign of aggression, dominance, or a challenge.

5. Nasal Obstruction: In some individuals, nostril flaring may occur as a compensatory mechanism in response to nasal obstruction or congestion. By widening the nasal passages, they can maintain adequate airflow despite the obstruction.

6. Respiratory Issues: In some cases, chronic nostril flaring can indicate underlying respiratory conditions. For example, it can be associated with conditions like allergies, asthma, or nasal polyps.

7. Sniffing and Smelling: Flaring nostrils is often accompanied by sniffing. Sniffing helps move more air through the nasal cavity and bring the odorous molecules in closer contact with olfactory receptors, thus aiding in the process of smelling.

8. Breathing During Exercise: During intense physical activity, the body's demand for oxygen increases. Flaring nostrils allow for increased airflow and oxygen intake to support the higher energy requirements of the muscles.

However, it's important to note that nostril flaring should not be confused with nasal flaring, which is a medical condition characterized by the widening and dilation of the nostrils, and is often associated with an underlying respiratory problem.