Haven't been to a Barber for 20 years or so, set of Clippers, Number 4 all over head and Number 3 for beard, OH does the back of neck every now and again, job done.
Anyway, doesn't a decent Barber Shampoo before cutting nowadays?
Here in the U.S. barbers and hairdressers are governed by extensive sanitation regulations administered by the State in which the business resides. I've been in the barber's chair when my barber was inspected… came out smelling like a rose (the barber, not me)!
Heads are shampooed before tools are put to them. Combs are regularly washed between clients and dipped in Barbicide. Scissors/clippers/razors are flamed & oiled regularly.