Question

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

Answer 1

Dust particles are foreign particles that are not required by our body. They may contain harmful bacteria or viruses which may infect us and can cause many diseases. So, our body tries to remove these unwanted waste particles.

Complete answer:
Our body, on a daily basis, interacts with many types of pathogen (diseases causing agents) which may infect us and many times become deadly to the human body. Like malaria, which is caused by plasmodium parasites, which is carried by mosquitoes.
Likewise, we encounter many such pathogens which are very dangerous to the human body. But our body is smart enough to protect itself, we have developed many protective systems for the body which help in fighting against these germs and give us a healthy life.
Whenever we inhale dust-laden, we sneeze to remove these dust particles which are not required by our body. These particles when interacting with nasal hairs, cause irritation in the lining of the nasal cavity which sends a message to the brain that some foreign particles are trying to enter which are immediately required to be expelled.
Thus, the brain gives command to the nasal cavity to initiate sneezing. Thus, we can conclude that when we inhale air with dust-laden, we sneeze to remove unwanted dust particles.

Note:
Many microbes are present in the air itself. When we inhale air, it is very important to ensure that no microbe or unwanted material goes inside the body. Our nasal cavity contains small hairs, which are very important in air purification, which we inhale for respiration.