Hi Renata, I have used TENS post shingles. I don't know that age precludes use, unless they have a loss of cognitive faculty. The usual advice would apply when using TENS i.e. not on carotid sinus/eyes/genitals/area of diminished sensation/rapidly dividing tissue, not used in bath/shower/swimming/driving/operating machinery/asleep/while pregnant. It would be wise to check with her physician regarding skin Ca and the use of TENS.
Regards
Robotone