The drama on transport vehicles in Cameroon

Transport buses covering long distances in Cameroon have one common characteristic. What we observe is the sale of 'medicinal products' on board buses linking major cities of the country.
What's so dramatic about this phenomenon is the fact that people inhale substances they don't know, even when they don't have 'any major health problem'.
I observed a strange sight on Saturday on board a bus travelling from Yaoundé to Ebolowa.
A certain man in his forties or so got on the bus and started his campaign. Shortly afterwards, he offered some powdery substance to a few passengers to inhale.
They took the substance and did as prescribed.
Behold, they started sneezing as soon as possible. For the next one hour or more, the sneezing was unstoppable.
Among them was a little girl of about eight years old. She was the first to start sneezing. And she did it so dramatically that most passengers turned to look at her occasionally. In the end she fell asleep.
And what shocked me  most was the fact that the products , for they were many, were never bought, not ev
en by those who had tasted one of them. And the disappointed 'doctor' jumped off the bus after a short drive.
That's part of the bus hospital saga.
On nearly every bus, you find someone who claims to blend traditional African medicine with science.
Some even limit themselves only to modern or Western medicine which they sell to passengers without any consultation or diagnosis.
Toothpaste, toothbrush, biscuit, candy, and a host of other products are also sold on buses.