In a lady of 56 years, H Zoster re occurred at dermatoms where it occurred 16 years back. On previous episode I treated with Acyclovir, this time with famcivir 800 mg bid. Query is: Can it reappears? Is there any special precaution to be exercised?

Any investigation  from neurological side? She became widow at age 41 years now serving at place of her husband.