body hygiene is must for health.otherwise they will land up with many skin diseases,gastric problems,hair fall
,dandruf and itcying. As he is a smoker all other infections affecting other organs of the body have already been showing symptoms like coughing and vomitting.
Try to educate him and create awareness regarding healthy and hygienic habits
for his good health. tell him HEALTH IS WEALTH. If he doesnt agree then try keep your self away from that environment to protect your self from the disease causing organisms.Children are more susceptible to infections so you must try to keep child away. It affects mental and physical health of the child.