How do you manage itchy skin in the elderly?

My mother is 82 years old and she says her whole body itches.

I've heard that as you get older, your skin gets dry and itchy.

I think it's too severe.

I'm worried because you keep scratching so much that you're about to get a bruise.

Of course, I tried taking dermatological medication prescribed by a dermatologist and applying moisturizing cream at home.

It doesn't work at all.

When I take the medicine, the itchiness is relieved for a while, but when I stop taking the medicine, the itchiness returns.

Are there any people like my mother?

Which department should I go to and get tested to find out the reason?

If anyone has tried this treatment, please give me some advice.

If you know any tips to help relieve itching, please let me know.