I have been performing microdermabrasion for quite a few months now and have had lots of very satisfied customers all seeing good improvements. However recently I treated a friend who I had previously treated without issues and this time she had a bad reaction to it. The following day her skin was still red and it has striping where I had moved the hand piece over her face. This is really upsetting me as I can't understand why it has happened when I haven't done anything differently. It was her time of the month and she had been under the weather s few days before but I wouldn't have expected that to make such a difference? Also the redness and dryness has subsided but the striping is still faintly visible 5 days later. What can I advise her?