I can understand your concerns,i would have asked you the age of your mother and any other medical illness if she had like Diabetes
problems or liver
disease? the duration of the itch,what aggravates it what relieves it? is this the first time she is suffering from it? is her skin very dry?
But unfortunately i cant so i want to exlain to you something here at this point,like its not necessary that a person having an itch is always due to something inside the skin,it acn be due to some internal problems in the body aswel.
AS we say all that itch is not scabies
always:) although scabies is also very common cause and cannot be ignored.
so my point is that she needs to see a dermatologist
so that he can review and examine her thoroughly and runs some blood test
if he likes and try to reach at the bottom of the cause.
I hoe i have made my point clear to you that treating the itch with anti allergics is not the solution,although there is no harm in using thenm for the timebeing,but all the local (environmental) and internal causes should be ruled out.
thanks alot and all the best.