Question

Why do we often sneeze when we inhale a lot of dust-laden air?

Answer 1

We often sneeze when we inhale a lot of dust-laden air to expel out these foreign particles. These particles get past the hair in the nasal cavity and irritate the lining of the nasal cavity which results in sneezing.
Sneezing is a type of defense mechanism used by our body to get rid of suspended pollutants if they gain entry into our respiratory system.