Greetings. Usage of hair fibres form reputed brands hould not cause problems that you are anticipating. However you should remember that hair fibres are a camouflage and the hair loss that is present will still be there and might even increase if you are not addressing it appropriately. Hair fibres are like covering up but meet and discuss more about gaining more volume and density to your scalp so that over a span of few months you may not need additional hair fibres.
Your dermatologist will decide a treatment plan for you after a consultation.
One needs to be patient with the treatment protocol as it takes months to see initial improvement.