What is chance of contracting hepatitis if one gets skin cut on neck of 4mm by hair trimmer at barbershop. what blood tests can be done to rule out?

Incredibly small: Licensed barbers and cosmetologists are required to clean instruments thoroughly between uses, including use of germ-killing cleaning fluids. Make sure the shop has all required licenses. There would be no reason to get a hepatitis test after a small skin cut if proper cleaning methods were used. Ask your doctor about getting vaccinated against hepatitis b if you aren't already.