When I wash my hair, I lose even more hair. That's why I try to avoid washing my hair. Why is that?

It is a fallacy to assume that washing your hair alone triggers or increases hair loss. It is completely normal to spontaneously lose more hair both when combing and washing.

This is due to handling: the mechanical action exerted on the hair (brush or comb pulls lightly on the hair, rubbing in shampoo, etc.) causes telogen hairs to come loose. In other words, hair in the shedding phase that would have fallen out anyway. If the hair is washed regularly several times, this effect is distributed.

However, if the hair is only washed once a week, it is not distributed over several days and the telogen hairs fall out all at once.